@article{benson_malloy_steed_christensen_fairchild_davis_2017, title={Zona pellucida protein B2 messenger ribonucleic acid expression varies with follicular development and granulosa cell location}, volume={96}, ISSN={["1525-3171"]}, DOI={10.3382/ps/pex126}, abstractNote={ABSTRACT The freshly ovulated ovum in avian species is surrounded by a protein layer called the inner perivitelline layer (IPVL). The IPVL contains zona pellucida proteins and 6 distinct zona pellucida genes have been identified (ZPA, ZPB1, ZPB2, ZPC, ZPD and ZPX1) in the chicken. In the present research, the expression of the mRNA for ZPA, ZPB2, and ZPX1 was investigated in 2 lines of turkey hens selected for either increased egg production (E line) or increased body weight (F line). Theca and granulosa cell expression of the mRNA for ZPA and ZPB2 was also investigated in hierarchical and prehierarchical follicles from broiler breeder hens. Granulosa tissue was collected from F1 through F4 and F1 through F10 follicles in E line and F line hens, respectively. A one cm2 section of the granulosa layer around the germinal disc (GD) and an equivalent sized nongerminal disc (NGD) area was also collected from the F1 and F2 follicles from other hens from each genetic line. Granulosa and theca tissue was collected from hierarchical and prehierarchical follicles of broiler breeder hens. Total RNA was extracted from the samples. Minor groove‐binding probes and primers for detecting ZPA, ZPB2, and ZPX1, were made for real‐time PCR analyses. Expression of ZPA, ZPB2, and ZPX1 was detected in all follicle sizes from both genetic lines of hens. No significant differences in ZPA and ZPX1 mRNA expression were detected between the GD and NGD granulosa cells. However, the expression of the mRNA for ZPB2 was significantly greater in the GD granulosa cells when compared to the NGD granulosa cells in F1 and F2 follicles from E line and F line hens. In broiler breeder hens, the mRNA expression of ZPA and ZPB2 was greatest in the smallest prehierarchical follicles. The results suggest that higher expression of ZPB2 in the germinal disc area may be important for the preferential binding of sperm to this region of the IPVL.}, number={9}, journal={POULTRY SCIENCE}, author={Benson, A. P. and Malloy, M. N. and Steed, J. R. and Christensen, V. L. and Fairchild, B. D. and Davis, A. J.}, year={2017}, month={Sep}, pages={3414–3421} }
 @article{temple_miyamoto_mehta_capitini_von stetina_barnes_christensen_horton_spears_orndorff_2010, title={Identification and Characterization of Two Bordetella avium Gene Products Required for Hemagglutination}, volume={78}, ISSN={["1098-5522"]}, DOI={10.1128/iai.00140-10}, abstractNote={ABSTRACT}, number={6}, journal={INFECTION AND IMMUNITY}, author={Temple, Louise M. and Miyamoto, David M. and Mehta, Manju and Capitini, Christian M. and Von Stetina, Stephen and Barnes, H. John and Christensen, Vern L. and Horton, John R. and Spears, Patricia A. and Orndorff, Paul E.}, year={2010}, month={Jun}, pages={2370–2376} }
 @article{christensen_2009, title={Development during the first seven days post-hatching}, volume={2}, ISSN={["1758-1567"]}, DOI={10.3184/175815509X430417}, abstractNote={The neonate has basic needs that must be satisfied at the time of hatching if survivability and maximum potential are achieved. Some of these basic needs are fresh air, clean water, proper feed, and heat. The developmental state at hatching of the neonate differs among all avian species (Nice, 1962). The post-hatching period for altricial neonates is more critical than for precocial birds because they hatch in a less mature state. Differing amounts of maternal care are therefore essential for each species (Nice, 1962). Although embryonic growth among species is very similar, no two physiological systems seem to mature at the same rate (Ricklefs and Starck, 1998). In addition, maturity may be a function of the egg conductance constant (Ar and Rahn, 1978), which is determined by egg mass, eggshell conductance (or functional properties) and the length of the incubation period (see Box 1 later), all of which may constrain neonatal maturity. When viewed energetically, the difference between maturity types resides in the different water concentrations in eggs and hatchlings, in the density of chemical potential energy in the dry matter of true hatchlings, and in the different amounts of energy transferred from the egg to the spare yolk (Ar et al., 1987). On the basis of species comparisons of posthatching growth of all birds (Lilja, 1983; Ricklefs, 1987), it has been suggested that the rate of growth after hatching is at least partially determined by the pattern of organ growth. It appears that a high rate of growth is correlated to early growth of ‘‘supply organs’’ (oesophagus, proventriculus, gizzard, intestines, heart and liver) at the expense of ‘‘demand organs’’ (breast, wings, legs and feathers). These changes begin very early in development (Lilja and Olsson, 1987), and Schmalhausen (1930) hypothesised that growth and organ function come into conflict when growth occurs too slowly or too rapidly. Even under the most optimum conditions, a newly hatched bird is not free from stress. This is impossible because the absence of stress is death (Selye, 1951). However, hatchlings possess abilities to cope with stress via adrenal cortical hormones (Davis and Siopes, 1989). Hatchlings have different blueprints for growth and maturation that must occur within a predetermined time frame. Many times this blueprint does not include adjustments that need to occur in maturational and growth processes in an imperfect environment. The objective of this paper is to define a ‘‘physiologically normal’’ hatchling and to describe the principles involved in the maturation and growth of several organ systems during the initial stages of life. At least six physiological systems exist that require maturation during the last week of incubation or, in the case of altricial species, the initial days of life outside the shell. These systems are: (1) the circulatory system (heart and blood); (2) the kidney and body fluids system; (3) the digestive system; (4) body temperature regulation; (5) the respiratory system; and (6) the immune system. These systems are discussed here using published data to help clarify important points.}, number={1-2}, journal={AVIAN BIOLOGY RESEARCH}, author={Christensen, Vern L.}, year={2009}, pages={27–33} }
 @article{fasenko_robinson_christensen_2009, title={Effects of long term storage on the egg, embryo and chick}, volume={2}, ISSN={["1758-1559"]}, DOI={10.3184/175815509X431858}, abstractNote={When most people think of a chicken egg, they think of something nutritious to eat. From an avian embryo’s point of view the egg provides the same function. At the time the egg is laid, if the oöcyte has been successfully fertilised, almost all of the nutrients required for the embryo to grow and develop are enclosed within the egg. There are two main elements missing; one is oxygen and the other is heat. The importance of both of these factors in embryonic growth and development are addressed elsewhere in this book (see French, 2002; Ar and Deeming, 2002). In most commercial poultry breeding operations, hatching eggs are produced by flocks of breeders housed in barns. Male and female broiler breeders are housed together so that natural mating can occur, while turkey breeder hens are housed separately from the toms and therefore must be artificially inseminated. Most broiler breeder eggs are laid in nests and collected by mechanical belts while turkey breeder eggs are still hand-collected. Irrespective of the method of insemination or egg collection, once the eggs are collected they are stored in on-farm cool stores, usually for a few days, until they can be transported to the hatchery. This is done as daily egg transport from the breeder farms to the hatchery would be inefficient. Once transported to the hatchery, the eggs are again stored in large egg stores. Egg storage at the hatchery usually occurs for two reasons. First, hatching eggs are stored until enough eggs are available to fill large incubator racks. Second, stock-piling of eggs occurs in anticipation of fluctuations in egg production or demand for broiler chicks during the production year. Storage of fertile eggs both on farm and at the hatchery occurs at temperatures below 21 C. This can prevent the growth of bacteria, but the main purpose is to stop development of the very young embryo. After oviposition, temperature is the primary catalyst which influences embryonic development (see French, 2002). As assessed by microscopic embryonic staging methods (Eyal-Giladi and Kochav, 1976), storage of fertile Single Comb White Leghorn eggs for various lengths of time at 14 C stopped all observable embryonic development (Table 1; Fasenko et al., 1992). Using a similar microscopic staging technique developed for turkey embryos (Gupta and Bakst, 1993), it was shown that turkey embryonic development during storage for 3, 7 or 14 days at 15 C continued from Stage 7 (the stage most common at the time of lay) to a Stage of 8, and then ceased (Bakst and Gupta, 1997). The minimum temperature above which embryonic development occurs (physiological zero) has been reported at two different levels. Edwards (1902) reported the minimum temperature for embryonic development to be 21 C, while Funk and Biellier (1944) found this minimum temperature to be 28 C. Previous researchers have hypothesised that the minimum temperature for embryonic development is not the same for all developing tissues of the early growing embryo (Kaufman, 1948). Therefore the objective of storing eggs at temperatures well below physiological zero is to prevent abnormal growth of the embryo which could occur if eggs were held at temperatures between physiological zero and normal incubation temperatures of 37.5 C. The generally accepted optimal range for hatching egg storage in the industry is between 14 and 18 C. Different storage temperatures and conditions are recommended depending on the length of storage (See reviews by Proudfoot and Hamilton, 1990; and Meiijerhof, 1992). AVIAN BIOLOGY RESEARCH 2 (1/2), 2009 73–79}, number={1-2}, journal={AVIAN BIOLOGY RESEARCH}, author={Fasenko, Gaylene M. and Robinson, Frank E. and Christensen, Vern L.}, year={2009}, pages={73–79} }
 @article{cutchin_wineland_christensen_davis_mann_2009, title={Embryonic development when eggs are turned different angles during incubation}, volume={18}, ISSN={["1537-0437"]}, DOI={10.3382/japr.2008-00079}, abstractNote={SUMMARY Not turning eggs during incubation or turning at a reduced angle could potentially reduce the incidence of hot spots in machines, thereby lessening the chance of embryonic mortality and decreased hatchling quality caused by overheating. Not turning eggs can also allow more eggs to be placed in an incubator by designing the machine with trays closer together. However, eggs that are not turned during incubation exhibit a higher frequency of embryonic developmental deficiencies and a reduced hatch compared with turned eggs. An experiment was conducted to determine the effects of a reduced turning angle on embryonic and extraembryonic development. Turning eggs 15° caused an increase in embryonic mortality from d 11 to 16 and d 17 to 21 and an overall decrease in hatch when compared with turning eggs 45°. There was no difference in area vasculosa at d 3 but there was a reduced amount of subembryonic fluid at d 6. Overall, it was determined that a reduced turning angle decreases the hatch of fertile eggs.}, number={3}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Cutchin, H. R. and Wineland, M. J. and Christensen, V. L. and Davis, S. and Mann, K. M.}, year={2009}, pages={447–451} }
 @article{benson_christensen_fairchild_davis_2009, title={The mRNA for zona pellucida proteins B1, C and D in two genetic lines of turkey hens that differ in fertility}, volume={111}, ISSN={["1873-2232"]}, DOI={10.1016/j.anireprosci.2008.02.013}, abstractNote={The avian inner perivitelline layer (IPVL) contains zona pellucida protein-B1 (ZPB1), zona pellucida protein-C (ZPC) and zona pellucida protein-D (ZPD). These three proteins may be involved in sperm binding to the IPVL. ZPB1 is produced by the liver and transported to the developing preovulatory follicle, while ZPC and ZPD are synthesized and secreted by the granulosa cells of the preovulatory follicle. The mRNA of ZPB1, ZPC, and ZPD was investigated in two lines of turkey hens selected for over 40 generations for either increased egg production (E line) or increased body weight (F line). Total RNA was extracted from the liver and from 1cm(2) sections of the granulosa layer around the germinal disc and a nongerminal disc area of the F(1) and F(2) follicles of hens from each genetic line. Northern analysis was performed using chicken cDNA probes for all three ZP proteins. Hepatic mRNA for ZPB1 was greater (P<0.05) in turkey hens from the E line than the F line. Although, there was no difference in ZPC mRNA between the germinal disc and nongerminal disc region of the two largest follicles in E line hens, ZPC mRNA was greater in the nongerminal disc region compared to the germinal disc region in the two largest follicles obtained from the F line hens. There were no differences in ZPD mRNA between the germinal disc and nongerminal disc regions of the F(1) and F(2) follicles for either genetic line. The results suggest that the greater rates of fertility previously observed in eggs from the E line hens compared with the F line of hens may be related to differential amounts of the potential sperm binding proteins ZPB1 and ZPC.}, number={2-4}, journal={ANIMAL REPRODUCTION SCIENCE}, author={Benson, A. P. and Christensen, V. L. and Fairchild, B. D. and Davis, A. J.}, year={2009}, month={Apr}, pages={149–159} }
 @article{oviedo-rondon_small_wineland_christensen_mozdziak_koci_funderburk_ort_mann_2008, title={Broiler embryo bone development is influenced by incubator temperature, oxygen concentration and eggshell conductance at the plateau stage in oxygen consumption}, volume={49}, ISSN={["1466-1799"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-57849128060&partnerID=MN8TOARS}, DOI={10.1080/00071660802433149}, abstractNote={1. Four experiments were conducted to evaluate the effects of temperature (TEM) and oxygen (O2) concentrations during the last 4 d of incubation on bone development. Fertile eggs from two strains were obtained that either exhibited Low or High eggshell conductance (G). 1The mention of trade names in this publication does not imply endorsement of the products mentioned nor criticism of similar products not mentioned. 2. Four experimental cabinets provided either four TEM (36, 37, 38 or 39°C) or four O2 concentrations (17, 19, 21 or 23% O2). Data were analysed as a 2 × 2 factorial design. In the fourth experiment, two temperatures (36 and 39°C), two O2 concentrations (17 and 23%) and the same Low and High G strains were evaluated in a 2 × 2 × 2 factorial design. 3. Body weights (BW) and residual yolks were obtained, both legs were dissected. Femur, tibia and shank weights, length and thickness were recorded. Relative asymmetry (RA) of each leg section was calculated. 4. The results indicated that elevated TEM during incubation increased RA between the two legs, mainly in the Low G strain. Chickens at the lowest O2 concentrations had lighter and shorter tibias, lighter shanks, and increased RA of femur length compared to chickens in the 23% O2. In the fourth experiment no interactions were observed between O2 and TEM. High TEM depressed BW of Low G broilers, but no significant effect of treatments was observed on BW of High G broilers. Nevertheless, the high TEM or low O2 independently caused reduced femur and tibia weights and length, shank length and thickness, and both low O2 and high TEM together increased RA in shank weight. 5. These results suggest that late incubation conditions affect long bone development in broilers.}, number={6}, journal={BRITISH POULTRY SCIENCE}, author={Oviedo-Rondon, E. O. and Small, J. and Wineland, M. J. and Christensen, V. L. and Mozdziak, P. S. and Koci, M. D. and Funderburk, S. V. L. and Ort, D. T. and Mann, K. M.}, year={2008}, pages={666–676} }
 @article{oviedo-rondon_small_wineland_christensen_grimes_funderburk_ort_mann_2008, title={Effects of incubator temperature and oxygen concentration during the plateau stage of oxygen consumption on turkey embryo long bone development}, volume={87}, ISSN={["1525-3171"]}, DOI={10.3382/ps.2007-00470}, abstractNote={Temperature (TEM) and O(2) concentrations during the plateau stage of oxygen consumption are known to affect yolk utilization, tissue development, and thyroid metabolism in turkey embryos. Three experiments were conducted to evaluate these incubation effects on long bone development. Fertile eggs of Nicholas turkeys were used. In each trial, standard incubation conditions were used to 24 d, when the eggs containing viable embryos were randomly divided into 4 groups. Four experimental cabinets provided 4 TEM (36, 37, 38, or 39 degrees C) or 4 O(2) concentrations (17, 19, 21, or 23% O(2)). In the third experiment, 2 temperatures (36 and 39 degrees C) and 2 O(2) concentrations (17 and 23%) were evaluated in a 2 x 2 factorial design. Body and residual yolk weights were obtained. Both legs were dissected, and shanks, femur, and tibia weights, length, and thickness were recorded. Relative asymmetry of each leg section was calculated. Chondrocyte density was evaluated in slides stained with hematoxylin and eosin. Immunofluorescence was used to evaluate the presence of collagen type X and transforming growth factor beta. Hot TEM caused reduction of tibia weights and increase of shank weight when compared with cool TEM. The lengths of femur, tibia, and shanks were reduced by 39 degrees C. The relative asymmetry of leg weights were increased at 38 and 39 degrees C. Poult body and part weights were not affected by O(2) concentrations, but poults on 23% O(2) had bigger shanks and heavier tibias than the ones on 17% O(2). High TEM depressed the fluorescence of collagen type X and transforming growth factor beta. The O(2) concentrations did not consistently affect the immunofluorescence of these proteins. The chondrocyte density was affected by TEM and O(2) in resting and hypertrophic zones. In the third experiment, high TEM depressed BW, leg muscle weights, and shank length. Low O(2) reduced tibia and shanks as a proportion of the whole body. We concluded that incubation conditions affect long bone development in turkeys.}, number={8}, journal={POULTRY SCIENCE}, author={Oviedo-Rondon, E. O. and Small, J. and Wineland, M. J. and Christensen, V. L. and Grimes, J. L. and Funderburk, S. V. L. and Ort, D. T. and Mann, K. M.}, year={2008}, month={Aug}, pages={1484–1492} }
 @article{christensen_ort_nestor_havenstein_velleman_2008, title={Genetic control of embryonic cardiac growth and functional maturation in Turkeys}, volume={87}, ISSN={["1525-3171"]}, DOI={10.3382/ps.2007-00363}, abstractNote={Turkey experimental lines E (selected 44 yr for increased total egg production) and F (selected 38 yr for increased 16-wk BW) were mated reciprocally with the randombred control lines from which they were derived (RBC1 and RBC2, respectively), and the pureline and reciprocal cross poults were compared for their BW, heart weight, heart rates, myocardial glycogen and lactate concentrations, and plasma creatine kinase (CK) and lactate dehydrogenase (LDH) activities. The CK and LDH were used as indicators of cardiac insufficiency. Orthogonal contrasts of the data from the pureline and reciprocal cross data were used to estimate additive genetic effects, reciprocal effects (confounded maternal and sex-linked effects), and heterosis for each of the traits measured. Long-term selection for increased egg production in the E line has reduced embryo heart weight and has altered the energy metabolism of the myocardium. The differences in energy metabolism may be due to the more rapid heart rates. Conversely, long-term selection for increased 16-wk BW has significantly decreased the heart rate of F line embryos and has not changed the weight of the heart relative to the BW until the embryo has passed through the plateau stage. The F line embryos show a different energy metabolism that relies much more on gluconeogenesis. Embryo deaths occur more frequently in turkey embryos when the energy metabolism of the myocardium shows elevated glycogen to lactate ratios as it did in the pure E and F lines.}, number={5}, journal={POULTRY SCIENCE}, author={Christensen, V. L. and Ort, D. T. and Nestor, K. E. and Havenstein, G. B. and Velleman, S. G.}, year={2008}, month={May}, pages={858–877} }
 @article{christensen_havenstein_ort_mcmurtry_nestor_2007, title={Dam line and sire line effects on turkey embryo survival and thyroid hormone concentrations at the plateau stage in oxygen consumption}, volume={86}, ISSN={["1525-3171"]}, DOI={10.1093/ps/86.9.1861}, abstractNote={Inheritance of embryo thyroid function was measured in lines of turkeys. Two lines that had been selected for either increased egg production (E) or increased 16-wk BW (F) and their respective randombred controls (i.e., RBC1 and RBC2) were examined. Reciprocal crosses of dams and sires from each selected line and its randombred control were made to estimate sire line and dam line effects. Orthogonal contrasts were used to determine if the differences found were due to the presence of additive, nonadditive, or maternal, sex-linked, or both, gene effects. With the data involved, sex-linkage and maternal effects could not be separated. Embryo survival was measured for all lines and their reciprocal crosses. Crossing the RBC1 sire and E dam also resulted in better embryo survival and lower death losses at pipping than for the other cross- or purelines. Reciprocal crosses of the F and RBC2 lines showed better total embryo survival, and they survived pipping better than the F or RBC2 purelines. Thyroxine (T(4)) and triiodothyronine (T(3)) concentrations differed between the reciprocal crosses at external pipping, but the effects were inconsistent for the 2 data sets. Reciprocal tests indicated that maternal, sex-linked, or both, effects were present for T(3) concentrations at internal pipping in the E and RBC1 lines and at external pipping for the F and RBC2 lines. Reciprocal effects were significant for T(4) at internal pipping for both data sets. The RBC1 sire embryos had significantly higher T(3):T(4) ratios than the E line sire embryos at internal and external pipping, and the pureline RBC1 embryos had consistently higher ratios than the pureline E embryos. The differences for the T(3):T(4) ratios between these 2 lines at internal pipping, external pipping, and hatch appeared to be consistently additive in nature, although significant nonadditive or heterotic effects were present for the ratio at external pipping. Similar effects on the T(3):T(4) ratio were observed for the F and RBC2 lines at external pipping.}, number={9}, journal={POULTRY SCIENCE}, author={Christensen, V. L. and Havenstein, G. B. and Ort, D. T. and McMurtry, J. P. and Nestor, K. E.}, year={2007}, month={Sep}, pages={1861–1872} }
 @article{hoffman_benson_christensen_fairchild_davis_2007, title={Follicular development and expression of the messenger ribonucleic acid for the inhibin/activin subunits in two genetic lines of turkey hens that differ in total egg production}, volume={86}, ISSN={["0032-5791"]}, DOI={10.1093/ps/86.5.944}, abstractNote={The characterization of the follicular hierarchy and the expression of the mRNA for the inhibin/activin subunits was investigated in the follicles of 2 lines of turkey hens selected for over 40 generations for increased egg production (Egg line) or increased body weight (Growth line). The follicular hierarchies of 6 hens from the Egg and Growth lines were characterized in middle (45 wk of age) and late production (58 wk of age). Relative follicular weights for individual hierarchical follicles (>12 mm), pooled small yellow follicles (5 to 12 mm), and large white follicles (2 to 5 mm) were calculated. Total RNA was extracted for Northern blot analysis from individual granulosa cell layers of the F1 through F4 follicles, and from the combined granulosa and theca layers of small yellow follicles and large white follicles from an additional 6 hens from each genetic line. Egg line hens displayed a more distinct follicular size hierarchy than Growth line hens at 45 and 58 wk. Although total follicular weight relative to body size was greater at 45 and 58 wk of age for the Egg line hens than the Growth line hens, the total number of hierarchical follicles was greater in the Growth line hens at 45 and 58 wk of age. Expression of follistatin and the inhibin beta(B)-subunit was highest in nonhierarchical follicles, whereas the expression of the inhibin alpha- and beta(A)-subunits was highest in the hierarchical follicles. The inhibin alpha- and beta(A)-subunit mRNA expression pattern in the 4 largest follicles of the Growth line hens was not similar to the Egg line hens or characteristic of laying hens that have a high rate of egg production. The unusual inhibin subunit mRNA expression in the largest hierarchical follicles of the Growth line hens may account for their development of an abnormal follicular size hierarchy and for their poor egg production.}, number={5}, journal={POULTRY SCIENCE}, author={Hoffman, J. B. and Benson, A. P. and Christensen, V. L. and Fairchild, B. D. and Davis, A. J.}, year={2007}, month={May}, pages={944–952} }
 @article{christensen_ort_nestor_velleman_havenstein_2007, title={Genetic control of neonatal growth and intestinal maturation in turkeys}, volume={86}, ISSN={["0032-5791"]}, DOI={10.1093/ps/86.3.476}, abstractNote={Turkey experimental lines E (selected 44 yr for increased egg production) and F (selected 38 yr for increased 16-wk BW) were mated reciprocally with the randombred control lines from which they were derived (RBC1 and RBC2, respectively), and the pure line and reciprocal cross poults were compared according to their hatch, 3- and 7-d BW, jejunum weight, jejunum length, and jejunal maltase and alkaline phosphatase activities. Orthogonal contrasts of the data from the pure line and reciprocal cross-poult data were used to estimate additive genetic effects, reciprocal effects (confounded maternal and sex-linked effects), and heterosis for each of the traits measured. Body weights at hatch and at 3 and 7 d of age were increased in the F line relative to the RBC2 line and were decreased in the E line relative to the RBC1 line. The genetic changes from long-term selection in the E and F lines have had concomitant effects on jejunum growth and function that parallel the changes in growth rate. The increased BW of the F line poults and the decreased BW of the E line poults relative to their randombred controls may be due to increases in the absorption of nutrients because of greater intestinal mass rather than to differences in glucose digestion. Concomitant changes in egg weight in the 2 selected lines appear to have resulted in maternal effects that have significantly affected neonatal BW and digestive system maturation.}, number={3}, journal={POULTRY SCIENCE}, author={Christensen, V. L. and Ort, D. T. and Nestor, K. E. and Velleman, S. G. and Havenstein, G. B.}, year={2007}, month={Mar}, pages={476–487} }
 @article{hamidu_fasenko_feddes_o'dea_ouellette_wineland_christensent_2007, title={The effect of broiler breeder genetic strain and parent flock age on eggshell conductance and embryonic metabolism}, volume={86}, ISSN={["1525-3171"]}, DOI={10.3382/ps.2007-00265}, abstractNote={The effect of genetic strain (Ross 308; Cobb 500) and parent flock age [young (29 wk), peak (Ross = 34 wk; Cobb = 36 wk), postpeak (40 wk), mature (45 wk), old (55 wk), and very old (59 wk)] on eggshell conductance and embryonic metabolism were examined. At each flock age, eggs from each strain were incubated for 21.5 d in individual metabolic chambers to measure embryonic O(2) intake and CO(2) output. From these data, the respiratory quotient (RQ) and metabolic heat production were calculated. Data were analyzed by the GLM procedure of SAS at P < or = 0.05. Neither strain nor flock age influenced conductance. Total embryonic O(2) consumption, CO(2) output, RQ, and metabolic heat production over the entire incubation period were not affected by strain. Daily differences existed between strains for embryonic O(2) intake (1, 7, 16, 17, 19, 20 d of incubation), CO(2) output (1 to 4, 16 to 20 d of incubation), and heat production (4, 7, 16 to 19 d of incubation). Embryos from young, mature, old, and very old flocks produced significantly more total embryonic heat over the entire 21 d (1,712, 1,677, 1,808, and 1,832, respectively) than embryos from peak (1,601) and postpeak (1,693) flocks. Average RQ for the entire incubation period was higher in embryos from mature flocks compared with all other flock ages. Daily differences among embryos from different flock ages were shown for O(2) consumption (all but d 8 of incubation), CO(2) production (all but d 7 and 9 of incubation), and heat output. The results showed that genetic strain and parent flock age influence daily embryonic metabolism, especially during the early and latter days of incubation. These daily differences coincide with the days of incubation having a higher incidence of embryonic mortality; these 2 factors may be related. Further investigation into the relationship between embryonic metabolic heat production and mortality during incubation may lead to the development of specific incubation conditions for different genetic strains and flock ages.}, number={11}, journal={POULTRY SCIENCE}, author={Hamidu, J. A. and Fasenko, G. M. and Feddes, J. J. R. and O'Dea, E. E. and Ouellette, C. A. and Wineland, M. J. and Christensent, V. L.}, year={2007}, month={Nov}, pages={2420–2432} }
 @article{christensen_fairchild_ort_2006, title={Dam and sire effects on sperm penetration of the perivitelline layer of eggs produced by two strains of commercial turkeys}, volume={15}, ISSN={["1056-6171"]}, DOI={10.1093/japr/15.1.82}, abstractNote={Abstract The reproductive performance of 2 commercial turkey breeder lines was examined using reciprocal crosses between sires and dams of each line. One line had been selected using artificial inseminations performed at biweekly intervals, whereas the second line had been selected using inseminations performed at weekly intervals. The hypothesis was proposed that sires and dams of the 2 lines differ because of different abilities for sperm to penetrate the inner perivitelline layer (IPVL) and fertilize eggs. Fertilized eggs to hatch poults for the experiment were obtained from the primary breeders and were incubated using conditions recommended by the industry. Hens (n = 72) and toms (n = 15) from each strain were identified and reared in preparation for a reproductive cycle using commercially accepted standards. Beginning just prior to the onset of egg production and at weekly intervals thereafter, half of the hens were inseminated with semen from males of the same line, whereas the remaining half received semen from the opposite line. Eggs were collected from the pens daily and set in incubators to determine fertility and embryo survival. At biweekly intervals 3 eggs per pen were used for counting sperm penetration holes in the IPVL. Data were collected for fertility, hatchability, and time that embryos died for each of the pens. Dam and sire affected IPVL penetration independently. A dam by sire interaction influenced fertility, whereas hatchability was affected only by dam. Thus, it is concluded that selection of dam and sires for commercial breeders alters IPVL sperm penetration ability of hens as well as egg-binding ability of sires.}, number={1}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Christensen, V. L. and Fairchild, B. D. and Ort, D. T.}, year={2006}, pages={82–88} }
 @article{christensen_grimes_rowland_ort_2006, title={Effect of chelated calcium proteinate fed in the maternal diet of turkey breeders on embryo cardiac physiology and poult quality}, volume={5}, ISBN={1682-8356}, DOI={10.3923/ijps.2006.337.343}, abstractNote={Embryo and hatchling survival diminish as turkey breeder hens age. Recent data indicated that a chelated calcium proteinate (CCP) additive given to turkey breeder hens improved embryo survival as hens aged but did not affect shell thickness. We hypothesized that the mechanism by which this occurred may be by improved functional shell quality and its consequent effect on cardiac physiology. To test the hypothesis, CCP was supplemented to the diet of Large White turkey breeder hens for a 25 week egg production period and compared with controls without supplementation. Eggshell conductance, conductance constants, poult growth and cardiac physiology were measured at weeks 10, 18 and 25 of production. Because elevated temperatures increase heart rates and reduce heart weight and survival, half of the eggs was incubated at 37.9°C whereas the remaining eggs were incubated at 37.5°C. Embryos and poults from the CCP group exhibited increased heart weights and improved cardiac health. The hatching poults from CCP-fed hens also grew faster for the first 3 d of life. We conclude that CCP improves eggshell conductance, and the subsequent eggshell conductance constant (k) of eggs from turkey breeder hens. The change in k improved embryo cardiac health and poult BW after hatching.}, number={4}, journal={International Journal of Poultry Science}, author={Christensen, V. L. and Grimes, J. L. and Rowland, R. D. and Ort, D. T.}, year={2006}, pages={337} }
 @article{croom_decubellis_coles_daniel_christensen_2006, title={Effect of in ovo peptide YY on the ontogeny of glucose transport in turkey poults}, volume={5}, ISBN={1682-8356}, DOI={10.3923/ijps.2006.128.133}, abstractNote={Previous studies in this laboratory have demonstrated that peptide YY (PYY) administration to turkey poults at d25 of incubation enhances intestinal Na-dependent active glucose uptake. This study was designed to further characterize the ontogeny of glucose transport in embryonic and hatchling poults and to investigate the effects of PYY on this process during development. In Trial 1, 20 turkey eggs were randomly selected at days 20, 23, and 26 of incubation, as well as the day of hatch. Hatchlings were cervically dislocated and the body weight, jejunal length and jejunal weight were recorded. Jejunal glucose uptake was estimated by measuring H-3-O-methyl-D-glucose accumulation in 2 mm jejunal rings in vitro. Jejunal O 3 2 consumption was measured in vitro on jejunal rings using an O probe. In Trial 2, 40 turkey eggs were 2 randomly selected at days 20, 23 and 25 of incubation and injected, via the air sac, with either 0.9% saline or 0.9 % saline plus 400 μg PYY/kg egg weight. Embryos from each treatment were harvested on days 23, 26 and day of hatch. Measurements and analyses on jejunal tissue were conducted as in Trial 1. In Trial 2, embryonic weight and jejunal weight adjusted for body weight increased (p<0.05) with stage of incubation, while adjusted jejunal length decreased (p<0.01). Active and total glucose uptake and jejunal O2 consumption increased with age (p<0.05). The energetic efficiency of glucose uptake increased (p<0.05) between d26 and hatch. In Trial 2, PYY failed to significantly affect body or jejunal weight, glucose absorption, and O consumption at any stage of development. PYY did however, decrease the efficiency of glucose 2 uptake at d26 and at hatch (p<0.05). In contrast to earlier investigations using higher dosages of PYY, this study demonstrated that in ovo PYY administration at 400 μg/kg egg weight has little effect of jejunal function in turkeys.}, number={2}, journal={International Journal of Poultry Science}, author={Croom, W. J. and Decubellis, J. and Coles, B. A. and Daniel, L. R. and Christensen, V. L.}, year={2006}, pages={128} }
 @article{wineland_christensen_yildrum_fairchild_mann_ort_2006, title={Incubator temperature and oxygen concentration at the plateau stage in oxygen consumption affects intestinal maturation of broiler chicks}, volume={5}, ISBN={1682-8356}, DOI={10.3923/ijps.2006.229.240}, abstractNote={Incubator temperature and oxygen concentrations were tested as factors determining the intestinal maturation of two lines of broiler chickens. One line was a Low G line selected because its eggs display low eggshell conductance. The second line was a High G line that grew at a reduced rate and its eggs show high eggshell conductance values. All eggs were incubated normally until the 18 day of development or the th beginning of the plateau stage in oxygen consumption. At that time the eggs were divided randomly and placed into experimental cabinets operating at 36, 37 38 or 39oC in experiment 1 or with 17, 19, 21 or 23% oxygen in experiment 2. In experiment 3, the best and worst conditions observed in experiments 1 and 2 were combined in a factorial arrangement. Body weight and intestinal maturation were measured by assaying for maltase and alkaline phosphatase activities in intestinal tissues. Increasing temperatures suppressed intestinal maturation whereas increasing oxygen concentrations enhanced intestinal maturation. When examined together in a factorial arrangement, it was clear that the effects of temperature and oxygen on the embryos were independent because they did not interact. The effects of temperature and oxygen were greater on Low G broiler embryos than they were on High G type embryos. It is concluded that incubator temperatures greater than 37o C, and oxygen concentrations less than 21% are detrimental to intestinal maturation in broiler chicks.}, number={3}, journal={International Journal of Poultry Science}, author={Wineland, M. W. and Christensen, V. L. and Yildrum, I. and Fairchild, B. D. and Mann, K. M. and Ort, D. T.}, year={2006}, pages={229} }
 @inbook{christensen_2005, title={Artificial insemination (poultry)}, ISBN={0911910506}, booktitle={Merck veterinary manual}, publisher={Whitehouse Station, N.J. : Merck}, author={Christensen, V. L.}, editor={Kahn, C.M. and Line, S.Editors}, year={2005} }
 @article{christensen_fairchild_ort_nestor_2005, title={Dam and sire effects on sperm penetration of the perivitelline layer and resulting fecundity of different lines of turkeys}, volume={14}, ISSN={["1056-6171"]}, DOI={10.1093/japr/14.3.483}, abstractNote={SUMMARY All birds studied thus far are able to store spermatozoa within their oviducts for periods that can vary from several days to weeks, depending upon the species. Turkeys have a relatively long storage period compared with chickens, an observation that leads to the suggestion that sperm residing within the oviduct may interact with sperm entering the oviduct from later inseminations. Multiple sources of sperm within the oviduct also lead to the hypothesis that sperm competition may be important for the maintenance of fertility and embryo livability in turkeys. The current study tested the hypothesis that selection for economically important traits in lines of turkeys may have an effecton sperm competition as measured bythe ability to hydrolyze holesin the perivitelline layer, fertilize, and produce viable offspring. Linesofturkeysselectedforeggproductionorrapidgrowthwerecomparedwiththeirrespective randombred control lines. Reciprocal crosses of dams and sires of the selected and control lines were made to determine inherent sire and dam roles in sperm competition. Selection for increased egg production increased hydrolysis of the perivitelline layer and improved fertility but decreased early embryo death while increasing embryo deaths at pipping compared with controls, and these effects were primarily determined by the dam. Selection for increased body weight has created an interaction between dams and sires for sperm hydrolysis of the inner perivitelline layer, fertility and embryo survival. Thus, we concluded that genetic selection for economically important traits may affect sperm hydrolysis of the perivitelline layer and the subsequent fertility, and embryo livability.}, number={3}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Christensen, VL and Fairchild, BD and Ort, DT and Nestor, KE}, year={2005}, pages={483–491} }
 @article{godwin_grimes_christensen_wineland_2005, title={Effect of dietary phosphorus and phytase levels on the reproductive performance of large white turkey breeder hens}, volume={84}, ISSN={["1525-3171"]}, DOI={10.1093/ps/84.3.485}, abstractNote={An experiment was conducted to determine the effect of dietary P levels and dietary phytase enzyme (E) inclusion on Large White turkey breeder hen reproductive performance from 31 to 62 wk of age. Hens were placed in a curtain-sided house with 48 pens (10 birds per pen; 8 pens per treatment) at 31 wk and were fed a breeder ration with treatments as follows: HP, dietary available P = 0.55%; HPE, HP + E; MP, dietary available P = 0.35%; MPE, MP + E; LP, dietary available P = 0.17%; and LPE, LP + E. Feed and water were available ad libitum for 28 wk of lay. Diets were fed in mash form, and all other nutrients were formulated to meet or exceed NRC requirements. All hens were photostimulated in January (31 wk) with 15.5 h of light daily. Production data were recorded on a pen basis. Individual bird BW and feed consumption, by pen, were determined at monthly intervals from 31 to 62 wk. Hens were observed for weekly reproductive performance for hen housed egg production, hen-day egg production, settable eggs, cumulative settable eggs, hens out of lay, and hen mortality and for biweekly performance for egg fertility, hatchability of all eggs, hatchability of fertile eggs, egg weight loss, conductance, conductance constant (k), and embryonic mortality. Egg weight, eggshell thickness, egg components, and albumen and yolk P were measured monthly. At 62 wk of age, hen tibia P, plasma P, total fecal P, and water-soluble fecal P were determined. Decreasing dietary P resulted in no decreases in reproductive performance for turkey breeder hens to 62 wk. Additionally, decreased dietary P resulted in decreased total fecal P and water-soluble fecal P. Feeding turkey breeder hens dietary phytase enzyme resulted in significantly fewer hens going out of lay; however, this was not reflected in hen housed egg production. It was concluded that phosphorus could be lowered in turkey breeder hen diets, compared with current surveyed industry levels, without impairing reproductive performance.}, number={3}, journal={POULTRY SCIENCE}, author={Godwin, JL and Grimes, JL and Christensen, VL and Wineland, MJ}, year={2005}, month={Mar}, pages={485–493} }
 @article{christensen_wineland_ort_mann_2005, title={Eggshell conductance and incubator ventilation as factors in embryo survival and poult quality}, volume={4}, ISBN={1682-8356}, DOI={10.3923/ijps.2005.818.826}, abstractNote={Eggshell conductance (G) and incubator ventilation (VENT) were hypothesized to affect embryo viability and growth of poults following hatching. Nearly 6,000 eggs were weighed on the day of oviposition to determine eggs of like weight but of different G. From the 6,000 eggs, 4,000 were selected that were within 2 standard deviations of the mean. The eggs were randomly divided equally between two incubator cabinets. One cabinet operated with a closed VENT and a second operated with it open. At the completion of the 24 day of development, all eggs were weighed a second time to determine eggshell G. Three groups were formed at that time exhibiting high (Hi), average (Avg) or low (Low) G. The eggs within each group were placed into hatching trays of 100 eggs each and placed into he same incubation cabinet for hatching. Weights were recorded for cardiac, hepatic and intestinal tissues, and blood was collected from each treatment. The tissues were subsequently assayed for energy substrates. Embryo viability was noted and growth was observed up to 6 wk of age. More embryos in eggs of Hi or Avg G survived than did those in Low G eggs, but neonates at 6 wk from Hi G eggs weighed less than those from Avg or Low G eggs. Low G embryos had reduced heart, liver and intestinal weight and function. Embryo thyroid hormone concentrations were elevated in Hi G eggs but suppressed by Low G and Closed VENT. Thus, in the developmental process of the embryonic turkey, G may determine energy balance and maturity of each hatchling and may affect its survival and growth rates following hatching.}, number={11}, journal={International Journal of Poultry Science}, author={Christensen, V. L. and Wineland, M. J. and Ort, D. T. and Mann, K. M.}, year={2005}, pages={818} }
 @article{suvarna_christensen_ort_croom_2005, title={High levels of dietary carbohydrate increase glucose transport in poult intestine}, volume={141}, ISSN={["1531-4332"]}, DOI={10.1016/j.cbpb.2005.03.008}, abstractNote={The hypothesis was proposed that the carbohydrate in the first diet fed to turkey hatchlings upregulates the glucose transport system. Heavy and light body mass poults were observed to determine differences in glucose transport and carbohydrate digestion. Poults were weighed immediately posthatching. Heavy poults were at least ±2 S.D. above the mean whereas light poults were at least ±S.D. below the population mean (62.5 ± 0.4). Each group was randomly assigned to one of two diets. One diet contained 50% carbohydrate and the remaining diet had 15% carbohydrate. Although the diets were isocaloric, differing carbohydrate (corn starch) and fat (cottonseed oil) content had significant effects on body masses within 3 days. Poults fed low carbohydrate weighed more than those on high carbohydrate perhaps because fat is a preferred energy substrate in the neonatal turkey. Greater carbohydrate in the diet increased glucose uptake and maltase activity compared to diets containing more fat. Heavier poults at hatching remained heavier at 3 days posthatching. No differences between body mass categories were noted in glucose uptake measurements. Thus, differences seen in growth rates may not be attributed to glucose transport in the jejunum. It is concluded that turkeys belong to the class of birds in which the poults respond to more carbohydrate in the diet by increasing plasma T3 concentrations, upregulating the glucose transport system, and increasing enzymatic activity as with maltase.}, number={3}, journal={COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY}, author={Suvarna, S and Christensen, VL and Ort, DT and Croom, WJ}, year={2005}, month={Jul}, pages={257–263} }
 @article{christensen_wineland_yildirum_fairchild_ort_mann_2005, title={Incubator temperature and oxygen concentrations during the plateau stage in oxygen uptake affect turkey embryo plasma T4 and T3 concentrations}, volume={4}, ISBN={1682-8356}, DOI={10.3923/ijps.2005.268.273}, abstractNote={Avian embryo thyroid responses to incubator temperature and oxygen concentrations during the plateau stage in oxygen consumption were measured. It was hypothesized that turkey embryo thyroid responds in a limited way at this critical time to environmental conditions to modulate basal metabolism. Turkey embryos were exposed to one of four incubator temperatures (36, 37, 38 or 39 C) beginning on the o 25 day of incubation at the onset of the plateau, a time when plasma thyroxine (T ) and triiodothyronine (T ) th 4 3 concentrations normally increase. Blood was collected and thyroid hormone concentrations were measured at pipping (27 day) and hatching (28 day). Elevated temperatures depressed T and T concentrations and th th 3 4 increased the T to T ratios. In a second experiment four oxygen concentrations (17, 19, 21 or 23% oxygen) 3 4 were provided to the embryos using identical procedures. The 21% treatment significantly reduced T and 3 T at pipping compared to all other treatments, but 23% oxygen increased plasma T and the T to T ratio 4 3 3 4 compared to all other treatments. The 17% oxygen treatment elevated T compared to all other treatments. 3 At hatching, 23% oxygen elevated T and T to T ratios compared to all other treatments. When temperature 3 3 4 and oxygen treatments were applied together in a factorial arrangement, temperature and oxygen affected T and T hormone concentrations independently but did not interact. Therefore, we conclude that 3 4 temperature and oxygen are independent stimuli of the avian embryonic thyroid gland during the plateau stage, and that incubator temperature and oxygen concentrations can modulate development of turke y embryos by changing plasma T and T concentrations. 3 4}, number={5}, journal={International Journal of Poultry Science}, author={Christensen, V. L. and Wineland, M. J. and Yildirum, I. and Fairchild, B. D. and Ort, D. T. and Mann, K. M.}, year={2005}, pages={268} }
 @article{fairchild_christensen_2005, title={Influence of hen age and number of inseminated sperm on the number of holes hydrolyzed in the inner perivitelline layer of turkey eggs}, volume={14}, ISSN={["1537-0437"]}, DOI={10.1093/japr/14.3.576}, abstractNote={Abstract Eggs from young turkey breeder hens have a higher rate of early embryonic mortality (EEM) than eggs from older hens. Preliminary field data indicated that increased sperm concentration decreased the incidence of EEM in eggs from young hens. Possible explanations for decreased EEM following insemination with more concentrated sperm may include altered sperm binding and hydrolyzing of the inner perivitelline layer (IPVL) of eggs from hens of different ages. The current study examined differences in the number of sperm penetration (SP) holes hydrolyzed in the IPVL in hens at 2 different ages when inseminated with 25, 50, 100, 200, 400, or 800 million viable sperm. Hens (12/treatment) were inseminated on d 14 and 21 after photostimulation (32 and 33 wk of age) and were inseminated again at 12 and 13 wk of egg production (44 and 45 wk of age). The SP holes hydrolyzed in the IPVL were counted in the 1,098 eggs produced in the 3 wk following each insemination period. The number of SP holes hydrolyzed in the IPVL was significantly (P ≤ 0.05) greater in younger hens than older hens. Furthermore, the number of SP holes was significantly greater (P ≤ 0.01) with the 400 and 800 million insemination doses as compared with the other 4 insemination doses. There was no interaction between hen age and sperm insemination dose. In conclusion, the absence of an interaction between hen age and insemination dose suggests that factors other than numbers of sperm binding to the IPVL influence EEM. These factors may be a combination of oviduct influences and IPVL properties that change as the hen ages.}, number={3}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Fairchild, BD and Christensen, VL}, year={2005}, pages={576–581} }
 @article{rivera_christensen_edens_wineland_2005, title={Influence of selenium on heat shock protein 70 expression in heat stressed turkey embryos (Meleagris gallopavo)}, volume={142}, ISSN={["1531-4332"]}, DOI={10.1016/j.cbpa.2005.09.006}, abstractNote={Heat shock protein 70 (hsp70) family of proteins, which functions as molecular chaperones, has been associated with tolerance to stressors in avian species. Selenium (Se) is an essential trace mineral incorporated into the selenoenzymes such as glutathione peroxidase (GSHpx). GSHpx reduces oxidized glutathione (GSSG) to reduced glutathione (GSH) in the GSH/GSSG antioxidant system and protects cells from oxidative damage. This study was conducted to examine if the relationship between dietary supplementation of selenium to turkey (Meleagris gallopavo) hens and the embryonic exspression of hsp70 and GSHpx activity in heat stressed embryos. Livers of embryos developing in eggs from turkey hens fed diets with or without supplemental Se were analyzed for hsp70 concentration and GSHpx activity before and after recovery from a heating episode. Before heat stress, hsp70 concentrations were equivalent in each treatment, but GSHpx activity was maximized in the SE treatment group. After recovery from the heating episode, hsp70 concentrations were significantly higher (P < 0.05) in the non-Se-supplemented groups, but in the Se-supplemented groups the hsp70 concentrations were not different from pre-stress concentrations. In the pre-stress Se-supplemented group, liver GSHpx activity was significantly higher than GSHpx activity in the non-Se-supplemented embryo livers, and in the livers from embryos recovering from heat stress, GSHpx activity in the non-Se-supplemented group was lower than the pre-stress activity and significantly lower than the GSHpx activity in liver from Se-supplemented embryos recovering from heat distress. Se supplementation to the dams resulted in a significant increase in their embryos and that condition would facilitate a decreased incidence of oxidative damage to cells. A more reduced redox status in embryos from Se-supplemented dams decreased the need for cellular protection attributed to stress induced hsp70 and presumably allows heat distressed embryos to resume normal growth and development than embryos from dams with inadequate selenium nutrition.}, number={4}, journal={COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY}, author={Rivera, RE and Christensen, VL and Edens, FW and Wineland, MJ}, year={2005}, month={Dec}, pages={427–432} }
 @article{christensen_fairchild_ort_2005, title={The relationship between sperm hydrolysis of the perivitelline layer and embryonic livability}, volume={14}, ISSN={["1056-6171"]}, DOI={10.1093/japr/14.1.60}, abstractNote={SUMMARY The hypothesis was proposed that altered sperm hydrolysis of the germinal disc area of the ovum affects embryonic survival. Genetics and damaged spermatozoa were the 2 factors tested. Both factors affect embryonic livability. The mechanism of sperm selection was proposed to be in the oviduct or at the ovum during fertilization. To test the hypothesis, sperm hydrolysis from the creation of holes in the perivitelline layer and embryonic mortality were compared in 3 lines of turkeys representing the past 50 yr of turkey genetics. In the newer lines compared with older, sperm hydrolysis decreased and embryo livability at the first week of embryonic development declined, but embryo livability during the fourth week improved. The same lines were inseminated with 0- or 24-h-stored semen. Although penetration of the perivitelline layer by fresh sperm cells declined in modern lines, penetration of 24-h-stored sperm cells did not. When inseminated with 24-h-stored semen, all 3 lines showed depressed embryo livability compared with fresh semen at wk 1 of embryo development but improved embryo livability at wk 4 of development. In experiment 2, specific comparisons of single-trait selected lines with unselected control lines indicated that selection for rapid growth has increased sperm hydrolysis of the perivitelline layer by 24-hstored sperm, but selection for increased egg production has not. In vitro sperm hydrolysis of the perivitelline layer was examined only for the growth-selected line in experiment 3. The in vitro technique was used to examine perivitelline layer hydrolysis without oviduct effects. The data indicated no differences in holes in the perivitelline layer for lines or sperm storage. Thus, the data suggest that a reduction in the penetration of sperm through the perivitelline layer results in improved embryo livability at wk 4 of development, but we saw no association with wk 1 embryo livability.}, number={1}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Christensen, VL and Fairchild, BD and Ort, DT}, year={2005}, pages={60–68} }
 @article{narushin_kempen_wineland_christensen_2004, title={Comparing infrared spectroscopy and egg size measurements for predicting eggshell quality}, volume={87}, ISSN={["1537-5129"]}, DOI={10.1016/j.biosystemseng.2003.12.006}, abstractNote={The objective of the undertaken research was to compare infrared spectroscopy (IRS) and egg size measurements for non-destructive evaluation of eggshell strength. For the infrared analysis of the eggs from broiler breeds Ross 508×Ross and Case×Ross, an infrared spectrometer equipped with an upward looking diffuse reflection accessory was used. Data were collected from 5000 to 640 cm−1 at a resolution of 2 cm−1. Infrared and egg size parameters were correlated with eggshell quality parameters obtained using invasive techniques. Shell thickness was best predicted by IRS (correlation coefficient 0·52 versus 0·32 based on size measurements). Shell fracture force, maximal deformation, and shell stiffness were predicted with comparable accuracy by both IRS and egg size parameters (correlation coefficients ranging from 0·24 to 0·42). IRS was also able to predict shell weight with reasonable accuracy (correlation coefficient 0·72). Data suggest that neither physical size measurements or IRS yield high-quality predictions of eggshell quality, but IRS, given its speed and ability to predict multiple parameters with one measurement appears the favourable technique to explore further.}, number={3}, journal={BIOSYSTEMS ENGINEERING}, author={Narushin, VG and Kempen, TA and Wineland, MJ and Christensen, VL}, year={2004}, month={Mar}, pages={367–373} }
 @article{christensen_wineland_yildirum_ort_mann_2004, title={Incubator temperature and oxygen concentration at the plateau stage affect cardiac health of turkey embryos}, volume={3}, ISBN={1680-5593}, number={2}, journal={Journal of Animal and Veterinary Advances}, author={Christensen, V. L. and Wineland, M. J. and Yildirum, I. and Ort, D. T. and Mann, K. M.}, year={2004}, pages={52} }
 @article{christensen_wineland_yildirum_ort_mann_2004, title={Incubator temperature and oxygen concentration at the plateau stage affects intestinal maturation of turkey embryos}, volume={3}, ISBN={1682-8356}, DOI={10.3923/ijps.2004.378.385}, abstractNote={The plateau stage in oxygen consumption of turkey embryos occurs at 25 and 26 days of incubation when many embryos die. The plateau stage creates hypoxia, hypercapnia and presents a paradox for growth and embryo metabolism. Prior to the plateau, vital tissues accumulate glycogen to ensur e embryonic survival through anaerobic metabolism during the plateau. Intestinal maturation at the plateau demands great amounts of energy. Therefore, the objective of the study was to define the temperature and oxygen concentrations at the plateau that affect intestinal maturation. Three experiments were conducted to test incubator conditions during the plateau stage and their affect on intestinal maturation. In Experiment 1, turkey embryos at the plateau stage were exposed to 36, 37, 38 or 39 C. In Experiment 2, embryos at the o plateau stage were exposed to 17, 19, 21 or 23% oxygen concentrations, and in Experiment 3, the extreme levels of temperature and oxygen treatments were combined to test interaction effects on intestina l maturation. Elevating temperature depressed intestinal weight but not length. The elevated temperature also depressed intestinal maltase and alkaline phosphatase activities indicating inhibited function. Increasing oxygen had little effect on intestinal weight or length, but hypoxia increased maltase and decreased alkaline phosphatase activities in hatchlings. When examined in a factorial arrangement, temperature and oxygen displayed independent effects on growth and function and did not interact. Thus, incubator temperature greater than 37 C and oxygen concentrations less than 19% during the plateau stage delay intestinal o maturation.}, number={6}, journal={International Journal of Poultry Science}, author={Christensen, V. L. and Wineland, M. J. and Yildirum, I. and Ort, D. T. and Mann, K. M.}, year={2004}, pages={378} }
 @article{christensen_davis_2004, title={Maternal dietary iodide influences turkey embryo thyroid function}, volume={3}, ISBN={1682-8356}, DOI={10.3923/ijps.2004.550.557}, abstractNote={An experiment was designed to examine a mechanism to improve embryonic survival following maternal thyroid hormone manipulation. Commercial turkey breeder hens were fed diets containing supplemental iodide to mimic changes in the maternal thyroid output during an egg production cycle (32 to 48 wk of age). Dietary iodide treatment depressed maternal blood thyroxine (T4) concentrations in a time-dependent manner. Dietary iodide depressed maternal blood 3, 5, 3'-triiodothyronine (T3) levels across all times examined. The maternal dietary treatment increased embryonic blood concentrations of T4 at 25 to 28 d of incubation but depressed blood concentrations of T3 only at 27 d of incubation. In a second trial, the same response was noted in maternal blood when the hens were fed additional iodide with no corresponding effects on T3 concentrations. The iodide treatment decreased embryonic T4 concentrations in the second trial as well but in a time-dependent manner. Iodide accelerated the increase in T4 concentrations coincidental with earlier pipping in eggs from iodide-fed dams compared with controls. The data indicate that the embryonic thyroid function during hatching is dependent upon the maternal thyroid in turkey dams, even though the embryo develops outside the maternal body.}, number={9}, journal={International Journal of Poultry Science}, author={Christensen, V. L. and Davis, G. S.}, year={2004}, pages={550} }
 @article{suvarna_christensen_ort_croom_2004, title={Ontogeny of intestinal glucose transport in heavy and light body weight turkey poults}, volume={3}, ISBN={1682-8356}, DOI={10.3923/ijps.2004.783.790}, abstractNote={Development of intestinal tissue was measured in newly hatched poults. Both anatomical and physiological measurements were made on poults produced by two half sibling sires with hens that were their full or half siblings. The poults from one sire (HBW) weighed more at hatching than those from the other sire (LBW). Survival of the heavier poults was poor indicating metabolic insufficiencies. A significant positive correlation was noted between hatchling body weights and blood glucose concentration (Christensen et al., 2000a), and this was accompanied by depressed gluconeogenesis in HBW poults. The hypothesis was proposed that the HBW poults with elevated plasma glucose concentrations might have greater glucose absorption from intestinal tissue than did the LBW poults. The data confirmed heavier weights in HBW poults than LBW, and HBW jejunum weight relative to body weight was less than that of LBW. The poults did not differ in intestinal length, glucose transport, maltase activities or plasma triiodothyronine and thyroxine or glucose concentrations. The HBW poults also utilized less yolk during development than did the LBW indicating that the HBW embryos rely more on gluconeogenesis for survival during development than do the LBW. It was concluded that the increased body weight of HBW poults compared to LBW may be due to increased absorption of all nutrients because of a greater intestinal mass relative to body weight rather than to differences in glucose digestion and uptake rates.}, number={12}, journal={International Journal of Poultry Science}, author={Suvarna, S. and Christensen, V. L. and Ort, D. T. and Croom, W. J.}, year={2004}, pages={783} }
 @article{fasina_garlich_classen_ferket_havenstein_grimes_qureshi_christensen_2004, title={Response of turkey poults to soybean lectin levels typically encountered in commercial diets. 1. Effect on growth and nutrient digestibility}, volume={83}, ISSN={["0032-5791"]}, DOI={10.1093/ps/83.9.1559}, abstractNote={Lectins are known to bind to the intestinal brush border membrane and induce antinutritional effects such as disruption of the brush border membrane (BBM) and reduced nutrient digestibility in laboratory rodents. Because soybean lectin (SBL) is usually present in poult starter diets, 2 similar experiments with starting turkey poults were conducted to investigate the effects of purified SBL on growth performance and nutrient digestibility. Experimental diets were a corn starch-casein based control (lectin-free) semipurified diet (PD), semipurified diets containing 0.024 or 0.048% soybean lectin (PDL, PDH), and a corn-soybean meal diet (SBD). Experimental diets were fed from hatch to 14 d. Antibodies specific for soybean lectin were detected in the serum of poults fed the PDL and PDH diets, implying that the SBL in these diets remained active in the digestive tract. Poults fed the control PD or SBD grew equally well. The 0.024% SBL level in PDL had no significant detrimental effect on any parameters assessed in the 2 experiments. In contrast, the 0.048% SBL level in the PDH gave inconsistent results for feed efficiency (FE) and brush border enzyme levels. For instance, on d 6 in experiment 2, poults fed the PDH had poorer FE (P < 0.05) compared with the control PD treatment, but had similar FE to poults fed the PD in experiment 1. In conclusion, SBL present at levels up to 0.024% of the diet would not cause antinutritional effect in turkey poults up to 2 wk of age.}, number={9}, journal={POULTRY SCIENCE}, author={Fasina, YO and Garlich, JD and Classen, HL and Ferket, PR and Havenstein, GB and Grimes, JL and Qureshi, MA and Christensen, VL}, year={2004}, month={Sep}, pages={1559–1571} }
 @article{christensen_ort_wineland_grimes_2004, title={Turkey sire effects on embryonic survival and physiology}, volume={3}, ISBN={1682-8356}, DOI={10.3923/ijps.2004.80.88}, abstractNote={Sire effects on turkey embryonic survival and growth are not well understood. In avian species, the sire may play only a minor role in embryonic growth as dam effects, mediated through physical and functional qualities of eggs, are thought to be the main determinants. Very little is known of separate dam and sire influences on embryonic survival. The hypothesis was proposed that sires from lines with different BW and embryonic survival rates when mated to an unrelated dam line would produce embryos with different survival, growth and metabolism. Sires from a line with light BW but good embryonic survival (LBW) or sires from a heavy BW line and poor embryonic survival (HBW) were mated to dams of the same unrelated line. Sires from the dam line were included as a control group (Controls). Hens were randomly assigned to sires and inseminated identically at weekly intervals with semen from the assigned sire line. Eight biweekly settings of eggs were placed into incubators to test embryonic survival rates among the sire lines. Tissues were sampled at designated intervals during the experiment to assess the physiological basis for embryonic survival. Contrary to our hypothesis, embryos from the HBW sire line had the best survival compared to LBW and Control. Although LBW poults were from smaller sires, they weighed more than HBW poults. During development LBW sire embryos stored greater amounts of glycogen and lactate in liver and muscle. No effects were seen in cardiac tissue. BW differences were related to greater yolk, but the differences in organ weights and metabolism were clearly related to sire. Thus, sire DNA may direct organ growth and function and influence embryonic survival.}, number={1}, journal={International Journal of Poultry Science}, author={Christensen, V. L. and Ort, D. T. and Wineland, M. J. and Grimes, J. L.}, year={2004}, pages={80} }
 @article{christensen_grimes_wineland_davis_2003, title={Accelerating embryonic growth during incubation following prolonged egg storage 1. Embryonic livability}, volume={82}, ISSN={["0032-5791"]}, DOI={10.1093/ps/82.12.1863}, abstractNote={The hypothesis was proposed that shorter incubation periods and faster growth rates for long-stored eggs would improve embryonic survival and poult hatchling quality. Increased incubation temperatures were tested for their efficacy in improving embryonic livability in fertilized eggs stored for 15 d prior to setting in the incubator compared to controls stored for only 3 d. Two temperature treatments were applied. In experiment 1, a 37.8 degrees C set point for dry bulb temperature was used to accelerate development for the initial 2 wk compared to the controls at 37.5 degrees C. Following treatment, the accelerated embryos were returned to the same machine as the controls. In experiment 2, higher temperature exposure was only for the initial week of incubation. The temperature and storage treatments were in a completely random 2 x 2 factorial arrangement of treatments. At the completion of 28 d of incubation, survival rates of all treatments were determined by opening all nonhatching eggs to differentiate truly fertilized eggs from unfertilized. Hatchability was determined by dividing the total number of poults on a hatching tray by the number of fertilized eggs on a tray. Incubator trays were the experimental unit. Tissues were sampled in both experiments to verify treatment effects on growth and metabolism. Hatching times were observed at 4-h intervals during the actual hatching process beginning at 25 d of incubation. It was concluded that delayed growth and depressed metabolism of fertilized turkey eggs stored for 15 d can be compensated for by exposure to higher incubation temperatures for the initial 1 or 2 wk of incubation.}, number={12}, journal={POULTRY SCIENCE}, author={Christensen, VL and Grimes, JL and Wineland, MJ and Davis, GS}, year={2003}, month={Dec}, pages={1863–1868} }
 @article{christensen_grimes_wineland_davis_2003, title={Accelerating embryonic growth during incubation following prolonged egg storage 2. Embryonic growth and metabolism}, volume={82}, DOI={10.1093/ps/82.12.1869}, abstractNote={The hypothesis was proposed that the improved embryonic livability observed when higher incubation temperatures were imposed on eggs stored for 15 d prior to setting might have basis in energy metabolism. To test the hypothesis, fertilized turkey eggs were incubated either for the first 2 wk of development (experiment 1) or only the first week of development (experiment 2) at 37.8 degrees C compared with controls incubated at 37.5 degrees C. In both experiments, eggs were stored for either 15 or 3 d prior to setting. Viable embryos were selected randomly from each storage-by-incubation period treatment combination at 25 to 28 d of incubation and were sampled for blood, heart, and skeletal muscle tissues. Tissues were weighed and assayed subsequently for glucose or glycogen content. In experiment 2, the randomly selected embryos from each treatment combination were sampled at 7, 14, 21, and 28 d of incubation. Embryos at 7 and 14 d were assayed on a whole body basis, whereas at 21 and 28 d the bodies were dissected, and heart, liver, and skeletal muscle tissues were weighed and assayed for glycogen and lactate. Blood samples were collected between 25 and 28 d of incubation as in experiment 1 and assayed for glucose, creatine kinase, lactate dehydrogenase, and thyroid hormone concentrations. In both experiments, accelerated development was noted due to higher temperature and enhanced embryonic carbohydrate metabolism, and elevated thyroid hormone concentrations were observed compared with controls. It was concluded that a possible mechanism for the improved livability of faster growing embryos observed after prolonged egg storage might be due to better utilization of carbohydrate.}, number={12}, journal={Poultry Science}, author={Christensen, V. L. and Grimes, J. L. and Wineland, M. J. and Davis, G. S.}, year={2003}, pages={1869–1878} }
 @article{coles_croom_daniel_christensen_taylor_2003, title={In ovo peptide YY administration and jejunal glucose transport in hatchling turkey poults: Effects of dosage and genotype}, volume={2}, ISBN={1682-8356}, DOI={10.3923/ijps.2003.1.6}, abstractNote={Two trials were conducted to investigate the efficacy of in ovo administration of various dosages of peptide YY (PYY) on jejunal glucose absorption in hatchling poults from two strains of turkeys, Egg Line (EL) selected for egg production and British United Turkey (BUT) selected for growth. In both trials, either 100 µl saline (1.025% w/v) or saline plus PYY were injected into the air cell of fertile EL and BUT line eggs at day 25 of incubation. At hatch, poults were euthanized by cervical dislocation, the jejunum removed and its weight and unstretched length recorded. Two to 4 mg cross-sections of the mid-jejunum were used to estimate active and passive glucose absorption using the accumulation of 3-O-methy-D-glucose (3OMG) in the presence and absence of phlorizin. In Trial 1, EL and BUT eggs were administered saline or saline plus 600 µg/kg egg wt, while in Trial 2, EL and BUT eggs were administered either saline or saline plus 300, 600, or 900 µg/kg egg wt. No differences were observed in hatchling body weights of poults from saline and PYY treated eggs from either line in both trials. In Trial 1, poults from EL treated eggs (600 µg/kg egg wt) had greater active jejunal 3OMG uptake compared with saline treated controls (332 vs. 270 ρmol/min/mg tissue, p<0.05, respectively). In Trial 2, poults from BUT eggs treated with 900 µg PYY/kg egg wt had greater (p<0.05) jejunal glucose transport than by the control group or the 600 µg PYY/kg egg wt group. Poults from EL eggs treated with PYY had non-significant increases in 3OMG uptake at all levels of PYY administration. BUT poults from eggs treated with 900 µg PYY/kg had heavier jejunums adjusted for body weight. In ovo PYY administration at day 25 of incubation increases active glucose transport in the intestinal tract of turkey poults, however, response and dosage varies with turkey line.}, number={1}, journal={International Journal of Poultry Science}, author={Coles, B. A. and Croom, J. and Daniel, L. R. and Christensen, V. L. and Taylor, I. L.}, year={2003}, pages={1} }
 @article{christensen_ort_grimes_2003, title={Physiological factors associated with weak neonatal poults (Meleagris gallopavo)}, volume={2}, ISBN={1682-8356}, DOI={10.3923/ijps.2003.7.14}, abstractNote={Management related deaths in turkey hatchlings remain a problem for turkey growers. The etiologies of such deaths also remain obscure. The hypothesis proposed by the current study was that weak poults identified by their characteristic flip-over behavior would differ physiologically from normal poults in a way that interferes with development of critical systems such as the cardiovascular and nervous system. Eight groups of 500 poults (from a 20-wk laying cycle) of the same breeder flock were examined. Each placement was in the same brooder house operated at identical conditions. Observations of "flip-over" poults were made at 6-h intervals for the initial wk of age. Identified poults (n = 12) were sacrificed and sampled immediately. Flip- over poults differed from controls only in depressed heart weight and plasma thyroid hormone concentrations. The identified poults did not differ from controls in body weight, liver weight, yolk weight, blood glucose or organ glycogen concentrations. In a second trial, reduced heart weights were noted along with reduced capability to maintain cardiac glycogen concentrations. The reduced heart weight or function may result in failure to provide nutrients for proper brain function. The data suggest that management to aid weak neonatal turkey poult deaths may need to focus on conditions fostering heart growth and function.}, number={1}, journal={International Journal of Poultry Science}, author={Christensen, V. L. and Ort, D. T. and Grimes, J. L.}, year={2003}, pages={7} }
 @article{christensen_ort_suvarna_croom_grimes_2003, title={Relationship of the eggshell conductance constant to intestinal physiology}, volume={2}, ISBN={1682-8356}, DOI={10.3923/ijps.2003.207.213}, abstractNote={The hypothesis was proposed that eggshell conductance constants (k) alter embryonic intestinal development and affect growth post hatching. Egg weight (EW), eggshell conductance (G) and length of the incubation period (IP), the three components of the conductance constant were changed to determine their effect on intestinal physiology. Eggs were selected based on EW and G properties. Half of the selected eggs were incubated using a single stage temperature profile to shorten IP in each of two experiments. EW, G and IP interacted in the first experiment to affect intestinal growth and metabolism. In Experiment 2, k reduced intestinal weight in embryos as well as poults. EW and IP affected the size and maturity of intestinal tissue at the time of hatching. Differences in EW, G and IP observed at hatching were shown to affect the growth of poults for the first week following hatching. Thus, k may act to reduce growth in poults by affecting intestinal maturation. It is suggested that large eggs with low permeability may be at risk for weak poults. This may be especially true when they are exposed to shorter IP.}, number={3}, journal={International Journal of Poultry Science}, author={Christensen, V. L. and Ort, D. T. and Suvarna, S. and Croom, W. J. and Grimes, J. L.}, year={2003}, pages={207} }
 @article{christensen_ort_grimes_2003, title={Relationship of the eggshell conductance constant to neonatal cardiac physiology}, volume={2}, ISBN={1682-8356}, DOI={10.3923/ijps.2003.220.228}, abstractNote={The hypothesis was proposed that changes in functional qualities of eggs, or the eggshell conductance constant (k), may affect cardiac weight and physiology and predispose poults to a weakened condition. Improved knowledge of this relationship may allow selection of k to optimize hatchling cardiac health. Egg weights (EW), eggshell conductance (G) and lengths of the incubation period (IP) (the three components of k) were manipulated to determine their effect on the heart. Eggs were selected based on EW and G in Experiment 1. In Experiment 2, eggs from the same strain were obtained from flocks of different ages so they differed in EW. Half of the eggs were exposed to increased temperature treatments resulting in shorter incubation periods (IP). Interactions of EW and G affected heart weight and metabolism in Experiment 1. In Experiment 2, imposing short IP on different EW reduced cardiac weights as well as elevated glycogen to lactate ratios in the heart. Post-hatching growth was also depressed by k due to interactions of EW and IP. Thus, k affects cardiac weight and function and may contribute to weak poults.}, number={3}, journal={International Journal of Poultry Science}, author={Christensen, V. L. and Ort, D. T. and Grimes, J. L.}, year={2003}, pages={220} }
 @article{crouch_grimes_christensen_krueger_2002, title={Effect of physical feed restriction during rearing on Large White turkey breeder hens: 3. Body and carcass composition}, volume={81}, ISSN={["0032-5791"]}, DOI={10.1093/ps/81.12.1792}, abstractNote={Large White turkey breeder hens were used to evaluate the effect of three different levels of physical feed restriction on subsequent body and carcass composition. The four feed treatments were 1) ad libitum fed throughout the study (CC), 2) feed restricted from 16 to 24 wk (CR), 3) feed restricted from 3 to 16 wk (RC), and 4) feed restricted from 3 to 24 wk (RR). Feed restriction was implemented so that RC and RR hens achieved a 45% reduction in BW compared to CC hens at 16 wk. From 16 to 24 wk, feed was allotted to RR and CR hens to maintain a slight increase in BW. At the completion of each restriction period, hens were gradually returned to ad libitum feeding. At 30 wk, hens were photostimulated for a 20-wk summer season egg production cycle. Restricted fed hens had increased moisture levels at 16 and 30 wk and decreased fat levels at 16, 30, 39, and 54 wk (P < or = 0.05). Absolute and relative weights of the pectoralis major muscle were greater in hens fed ad libitum through 43 wk (P < or = 0.05). There were no differences in the number of maturing yellow follicles due to treatment. However, restricted fed hens had higher peak egg production during early lay but decreased subsequent and cumulative egg production. Changes in egg production were associated with changes in breast muscle weight. Prolactin levels were greater in hens in-production compared to hens out-of-production; however, there were no differences due to feed treatment. In conclusion, further research on quantitative feed-restriction programs, which result in body weight reductions as described in this study, should address specific physiological and nutritional requirements and not be implemented as general programs.}, number={12}, journal={POULTRY SCIENCE}, author={Crouch, AN and Grimes, JL and Christensen, VL and Krueger, KK}, year={2002}, month={Dec}, pages={1792–1797} }
 @article{crouch_grimes_christensen_krueger_2002, title={Effect of physical feed restriction during rearing on large white turkey breeder hens: 1. Growth performance}, volume={81}, ISSN={["0032-5791"]}, DOI={10.1093/ps/81.1.9}, abstractNote={Large White turkey breeder hens were fed ad libitum (CC), feed-restricted from 16 to 24 wk (CR), feed-restricted from 3 to 16 wk (RC), or feed-restricted from 3 to 24 wk (RR). Feed restriction was implemented so that RC and RR hens achieved a 45% reduction in BW compared to CC hens at 16 wk. From 16 to 24 wk, feed was allotted to RR and CR hens to maintain a slight increase in BW. At the completion of each restriction period, hens were gradually released back to ad libitum feeding. At 30 wk of age, hens were photostimulated for a 20-wk summer season egg production cycle. Mean BW for all treatments were different (P < or = 0.05) at 16 and 30 wk. At the end of lay, hens on treatment CR were not different in BW from treatment CC hens, and treatment RR hens were not different in BW from treatment RC hens. Hens on treatment RR had the greatest BW gain and feed consumption leading into the production cycle. All treatment hens lost BW from the time of first egg until 47 wk of age. Hens on treatment CC lost significantly (P < or = 0.05) more relative BW (%) than those in any other treatment. Coefficient of variation for flock uniformity was similar for all treatments at time of photostimulation. At the end of the study, cumulative feed consumption was significantly less for restricted treatments: 86.5, 83.1, 75.8, and 70.7 kg/hen for treatments CC, CR, RC, and RR, respectively.}, number={1}, journal={POULTRY SCIENCE}, author={Crouch, AN and Grimes, JL and Christensen, VL and Krueger, KK}, year={2002}, month={Jan}, pages={9–15} }
 @article{crouch_grimes_christensen_krueger_2002, title={Effect of physical feed restriction during rearing on large white turkey breeder hens: 2. Reproductive performance}, volume={81}, ISSN={["1525-3171"]}, DOI={10.1093/ps/81.1.16}, abstractNote={Large White turkey breeder hens were used to evaluate the effect of three different levels of physical feed restriction on subsequent reproductive performance. The feed treatments were: 1) fed ad libitum throughout the study (CC), 2) feed-restricted from 16 to 24 wk (CR), 3) feed-restricted from 3 to 16 wk (RC), and 4) feed-restricted from 3 to 24 wk (RR). Feed restriction was implemented so that restricted-fed hens (RC and RR) achieved a 45% reduction in BW as compared to CC hens at 16 wk. From 16 to 24 wk, feed was allotted to RR and CR hens to maintain a slight increase in BW. At the completion of the respective restriction periods, hens were gradually returned to ad libitum feeding. At 30 wk of age, hens were photostimulated for a 20-wk summer season egg production cycle. Hens receiving RC and RR treatments laid significantly more eggs than did CC and CR hens for the first 5 wk of lay. However, once the house temperature increased to 26.7 to 29.4 C during 6 to 10 wk of lay, egg production of all hens decreased, resulting in a significant decrease in cumulative egg production for RR and RC hens compared to CC and CR hens. Egg and poult weights were less for RC and RR hens compared to those from CC and CR hens. In conclusion, age of breeder, season of implementation, and length of physical feed restriction have significant effects on the reproductive performance of turkey breeder hens.}, number={1}, journal={POULTRY SCIENCE}, author={Crouch, AN and Grimes, JL and Christensen, VL and Krueger, KK}, year={2002}, month={Jan}, pages={16–22} }
 @article{christensen_wineland_fasenko_donaldson_2002, title={Egg storage alters weight of supply and demand organs of broiler chicken embryos}, volume={81}, ISSN={["1525-3171"]}, DOI={10.1093/ps/81.11.1738}, abstractNote={Storage of fertilized eggs for more than 10 d prior to incubation decreases embryonic viability. The hypothesis was tested that embryos may grow differently following egg storage. Eggs from which embryos survived following storage (ST) were compared to eggs from a second line that did not (NOST). Three identical, independent trials were conducted using fertile eggs from both lines at two ages (peak lay and > 53 wk). Eggs were stored for 1 or 14 d prior to setting in the incubator. At 3-d intervals during development, embryos were carefully removed from the eggs, the yolks were excised and carcasses were weighed. Beginning at 12 d of incubation whole body, heart, liver and thigh tissues were weighed to assess allometric growth of supply (heart and liver) and demand (thigh muscle) tissues. Storage of eggs from both lines and from hens of both ages decreased BW differently throughout incubation. Line, Age and Storage interacted to affect embryonic BW and organ weights. Embryo weights were consistently heavier in NOST line eggs from older breeder flocks stored for 14 d than those from ST line eggs. It was concluded that extended storage of fertile eggs prior to setting affects embryonic growth to enhance survival.}, number={11}, journal={POULTRY SCIENCE}, author={Christensen, VL and Wineland, MJ and Fasenko, GM and Donaldson, WE}, year={2002}, month={Nov}, pages={1738–1743} }
 @article{christensen_wineland_fasenko_donaldson_2002, title={Egg storage effects on plasma glucose and supply and demand tissue glycogen concentrations of broiler embryos (vol 80, pg 1729, 2001)}, volume={81}, DOI={10.1093/ps/81.4.595}, number={4}, journal={Poultry Science}, author={Christensen, V. L. and Wineland, M. J. and Fasenko, G. M. and Donaldson, W. E.}, year={2002}, pages={595} }
 @article{christensen_davis_nestor_2002, title={Environmental incubation factors influence embryonic thyroid hormones}, volume={81}, ISSN={["0032-5791"]}, DOI={10.1093/ps/81.4.442}, abstractNote={Thyroid hormone responses in embryonic avian species are of two types, developmental and metabolic. Many studies have characterized the developmental function of the turkey embryonic thyroid, but few have characterized the metabolic function. Therefore, the purpose of this study was to describe the response of turkey embryonic thyroid hormones to three environmental factors. We proposed that embryonic thyroids from different genetic backgrounds would respond differently to changes in maternal diet and incubation temperature. Lines of turkeys known to have different embryonic growth and survival were examined in the current study. These eggs differ in egg weight, eggshell conductance, hatchling weight and organ maturity at the time of hatching. Eggs were produced throughout a 20 wk laying period and embryos were sampled at monthly intervals. Half of the hens producing the eggs were fed additional iodide in their diets, then, subsequently, half of each dietary treatment and line combination were incubated at either 36.8 C or 37.5 C to prolong the incubation period. Embryos were sampled during the final week of incubation when thyroid hormones become elevated to effect maturation and survival functions in turkey embryos. Embryonic thyroxine (T4) and triiodothyronine (T3) levels were assayed by RIA and compared among the treatments. Line, diet, and incubation period interacted to affect the levels of T4, T3 and T3 to T4 ratios in the turkey embryonic during late incubation. It was concluded that environmental factors can affect circulating thyroid hormone levels in turkey embryos, thus affecting metabolic functions, and the possibility exists to manipulate these circulating levels using environmental incubation conditions to improve hatchability.}, number={4}, journal={POULTRY SCIENCE}, author={Christensen, VL and Davis, GS and Nestor, KE}, year={2002}, month={Apr}, pages={442–450} }
 @article{fairchild_christensen_grimes_wineland_bagley_2002, title={Hen age relationship with embryonic mortality and fertility in commercial turkeys}, volume={11}, ISSN={["1056-6171"]}, DOI={10.1093/japr/11.3.260}, abstractNote={Abstract The purpose of this study was to examine embryonic mortality in turkey eggs from hens of two ages and to report values that minimize the error of wrongly distinguishing between early embryonic mortality (EEM, Days 1 to 7 of incubation) and unfertilized eggs. Three hatch residue breakouts were performed at each of two commercial turkey hatcheries for a total of six hatches. Nicholas Large White turkey eggs from two hen age groups (32 to 35 and 44 to 50 wk of age) were set in the same incubator that operated under the incubation profile of each hatchery. The EEM was significantly greater (P ≤ 0.0001) in younger hens when compared to older hens. This was true for mortality prior to blood formation and mortality following blood formation. Hatchability, percentage internal pips, and live pips were not different between the two hen ages. Prepip mortality and percentage dead pips were significantly (P ≤ 0.0001) greater in older flocks. Fertility and EEM occurring after blood formation were negatively correlated in younger hens, whereas mortality occurring before blood formation did not correlate with fertility in eggs from either hen age. Eggs from young hens tended to experience embryonic mortality earlier in incubation than eggs from older hens. The results suggest that hen age influences embryonic mortality in modern commercial turkeys and could be used as an experimental model for further study of embryonic mortality.}, number={3}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Fairchild, BD and Christensen, VL and Grimes, JL and Wineland, MJ and Bagley, LG}, year={2002}, pages={260–265} }
 @article{christensen_fairchild_2002, title={Maternal and environmental influence on fertility and embryonic survival}, volume={13}, ISSN={["1470-2061"]}, DOI={10.3184/147020602783698584}, number={3}, journal={AVIAN AND POULTRY BIOLOGY REVIEWS}, author={Christensen, VL and Fairchild, BD}, year={2002}, pages={133–137} }
 @article{carver_grimes_christensen_joyce_fairchild_fairchild_2001, title={A novel delivery of oxytetracycline in turkey breeder hens}, volume={45}, ISSN={["0005-2086"]}, DOI={10.2307/1592984}, abstractNote={A novel product (SQ12) for subcutaneous (SQ) injectable delivery of oxytetracycline (OTC) has been developed for use in livestock. SQ12 employs microfluidic spheres encasing OTC crystals, which allows for longer release of the OTC compared with other injectable antibiotics. The objectives of the study were to determine serum and tissue levels of SQ12 in turkey breeder hens to 14 days postinjection and to evaluate effects of SQ12 on reproductive status. Thirty photostimulated hens were housed in litter floor pens and provided with 14.5 hr of light per day in a curtain-sided facility. Six hens served as untreated controls. Twelve hens per treatment group received SQ injections in the neck with SQ12 at 11.4 (L dose group) or 22.7 mg/kg (H dose group) to assess low and high doses, respectively. Serum samples were obtained from each hen at predose and 6, 12, 24, 48, 72, 96, 168, 240, and 336 hr postinjection. All hens were euthanatized at 14 and 15 days postinjection. One-half of the hens in each treatment group were sampled (liver, lung, kidneys, and breast muscle) for tissue residue levels of OTC. The control group had no detectable OTC in serum or tissues at any sample collection time. There were no detectable serum levels of OTC in either treatment group prior to injection. The average serum concentrations of the L and H dose groups showed similar depletion curves although the H dose group was 42% higher at maximum concentration than the L group. Average tissue concentration of OTC for all tissues sampled from the H dose group was twice that of the L dose group. All tissue levels were below the OTC residue tolerance limit. SQ12 provided an extended source of OTC in serum of turkey breeder hens with no effect on reproductive status. SQ12 may provide for a novel treatment of bacterial infection in turkey breeder hens with longer lasting serum levels compared with other single injectable OTC products.}, number={2}, journal={AVIAN DISEASES}, author={Carver, DK and Grimes, JL and Christensen, VL and Joyce, KA and Fairchild, BD and Fairchild, AS}, year={2001}, pages={437–441} }
 @article{christensen_grimes_wineland_bagley_2001, title={Effects of turkey breeder hen age, strain, and length of the incubation period on survival of embryos and hatchlings}, volume={10}, ISSN={["1056-6171"]}, DOI={10.1093/japr/10.1.5}, abstractNote={SUMMARY Embryonic growth relationships exist for egg weight, eggshell conductance, and length of the incubation period. These relationships have been well established for comparisons of embryonic development across species; however, very little is known about these relationships within a species. The hypothesis was tested that survival of embryos in turkey eggs could be changed by manipulating incubation periods. Fertile eggs were obtained three times from the same breeder flocks (two strains). Two incubator temperature treatments were used to create two different incubation periods for the eggs. Eggs produced at 33 weeks of age hatched better at shorter incubation periods, eggs produced at 43 weeks of age hatched equally well at both incubation temperatures, and eggs produced at 54 weeks of age hatched better at longer incubation periods. Livability for 5 days in brooder houses was highly variable but indicated survival differences between strains. Additionally, longer incubation periods produced poults that lived better than did controls. The results suggest that the conductance constant principle, which describes the relationship among egg weight, length of incubation, and eggshell conductance, can be used in commercial hatcheries to improve embryo survival and poult quality.}, number={1}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Christensen, VL and Grimes, JL and Wineland, MJ and Bagley, LG}, year={2001}, pages={5–15} }
 @article{christensen_wineland_fasenko_donaldson_2001, title={Egg storage effects on plasma glucose and supply and demand tissue glycogen concentrations of broiler embryos}, volume={80}, ISSN={["1525-3171"]}, DOI={10.1093/ps/80.12.1729}, abstractNote={The hypothesis was tested that enhanced embryonic carbohydrate metabolism may enable embryos to survive egg storage effects. As lines of broiler breeders age, some lines resist detrimental effects of egg storage on embryonic survival, whereas others do not. Fertile eggs were obtained from two lines differing in storage ability. Eggs from each line by age group were stored for 1 or 14 d prior to setting. Eggs were distributed randomly into a single machine and incubated under standard conditions. Beginning at 17 d of incubation, immediately prior to the plateau stage in oxygen consumption, embryos from each of the treatment groups were sampled for BW, organ growth, glycogen concentration, and plasma glucose concentrations. Sampling continued through hatching. Plasma glucose concentrations increased significantly, and hepatic glycogen concentrations declined as embryos approached hatching. The rate at which glycogen was accrued into muscle and heart tissue displayed a significant three-way interaction among line, age, and storage. Embryos from the line that resisted storage mortality maintained greater glycogen concentrations in muscle and heart tissues than those from the line and age with diminished survival rates. It was concluded that embryonic survival rates differ following egg storage because of the ability of the embryo to accrue and maintain adequate carbohydrate for growth and function of vital demand tissues.}, number={12}, journal={POULTRY SCIENCE}, author={Christensen, VL and Wineland, MJ and Fasenko, GM and Donaldson, WE}, year={2001}, month={Dec}, pages={1729–1735} }
 @article{fasenko_christensen_wineland_petitte_2001, title={Examining the effects of prestorage incubation of turkey breeder eggs on embryonic development and hatchability of eggs stored for four or fourteen days}, volume={80}, ISSN={["0032-5791"]}, url={http://europepmc.org/abstract/med/11232999}, DOI={10.1093/ps/80.2.132}, abstractNote={Thirty-six hundred British United Turkey hatching eggs were used in two separate trials to test whether prestorage incubation (PRESI) treatments of 0, 6, and 12 h (Trial 1) or 0, 7, and 14 h (Trial 2) could improve the hatchability of eggs stored (17 C) for 14 versus 4 d. The development of the embryos (n = 30) was staged before and after exposing eggs to the various PRESI treatments. Embryonic development was also established after storage to ascertain whether embryonic development was occurring during storage. The remaining eggs in each trial were split into three groups (n = 500) and incubated for 28 d to examine embryonic mortality and hatchability. No changes were observed in embryonic development due to egg storage. Embryos were significantly more developed as the number of PRESI h increased; therefore, embryos from different PRESI treatments were placed in storage at different stages of development. Early mortality (1 to 7 d of incubation), mortality at internal and external pipping, and hatchability of fertile eggs were significantly reduced in eggs stored for 14 versus 4 d. The various PRESI treatments did not significantly affect the mortality or hatchability of eggs stored for 4 d. However, the hatchability of eggs incubated prior to storage for 12 h and then stored for 14 d was restored to the levels reported for eggs subjected to the treatment that represents the industry norm (0 h of PRESI and 4 d storage). These results indicate that embryos of eggs stored for 14 d, which have developmentally advanced to the stage of complete hypoblast formation (PRESI for 12 h), have a survival advantage over eggs stored for 14 d that have not been subjected to any PRESI.}, number={2}, journal={POULTRY SCIENCE}, author={Fasenko, GM and Christensen, VL and Wineland, MJ and Petitte, JN}, year={2001}, month={Feb}, pages={132–138} }
 @article{christensen_2001, title={Factors associated with early embryonic mortality}, volume={57}, ISSN={["1743-4777"]}, DOI={10.1079/wps20010025}, abstractNote={This paper describes the patterns of embryonic mortality in poultry species and summarises the various causes of mortality. Descriptions of the morphological stages of development at each of these time periods are given. Data are presented describing factors affecting development at oviposition, egg storage and incubation.}, number={4}, journal={WORLDS POULTRY SCIENCE JOURNAL}, author={Christensen, VL}, year={2001}, month={Dec}, pages={359–372} }
 @article{coles_croom_daniel_christensen_eisen_2001, title={In ovo peptide YY administration improves body weight at hatch and day 3 in turkey poults}, volume={10}, ISSN={["1056-6171"]}, DOI={10.1093/japr/10.4.380}, abstractNote={SUMMARY Previous studies in our laboratory have demonstrated that in ovo administration of peptide YY (PYY) at Day 18 of incubation enhanced adjusted feed conversion ratio (AFCR) and BW gains of broilers during the first week post-hatch. Preliminary studies have also shown that in ovo PYY administration at Day 25 of incubation also increases jejunal glucose absorption in 1-d-old Nicholas turkey poults. The objective of this study was to further elucidate the effects of in ovo PYY administration on growth and feed conversion in two turkey lines: a commercial growth line (BUT; British United Turkey, UK) and the Egg Line. Eggs from both turkey lines were randomly placed in the same incubator. On Day 25 of incubation, 380 BUT and 440 Egg Line eggs were injected with 100 µL 1.025% saline (control) or 600 µg PYY/kg egg weight. At hatch, 168 poults from each treatment group were wing-banded, weighed, and randomly distributed across pens in four Petersime batteries. A standard turkey starter crumble feed and water were available ad libitum. Feed and birds were weighed on Days 3, 10, and 17 to determine BW gains and AFCR. Poults of both lines from PYY-treated eggs were heavier (P < 0.01) than controls at Day 3. This effect was not apparent at Days 10 and 17. A subset of birds from each treatment group was randomly chosen at Day 17 and sexed by dissection. At hatch and again at Day 3, there were no BW differences (P = 0.94 and P = 0.15, respectively) noted between sexes. Males were heavier at 10 and 17 d (P = 0.0001). These results suggest that PYY enhances poult weight and may attenuate differences in BW caused by gender during early post-hatch life.}, number={4}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Coles, BA and Croom, J and Daniel, LR and Christensen, VL and Eisen, EJ}, year={2001}, pages={380–384} }
 @article{christensen_mcmurtry_donaldson_nestor_2001, title={Incubation temperature affects plasma insulin-like growth factors in embryos from selected lines of turkeys}, volume={80}, ISSN={["0032-5791"]}, DOI={10.1093/ps/80.7.949}, abstractNote={An experiment was conducted to test the hypothesis that incubator temperature may affect circulating insulin-like growth factors (IGF-I and IGF-II). In prior studies, growth of turkey embryos was altered by increasing incubator temperatures. Interestingly, the embryonic growth of a growth-selected line (F) was reduced, whereas embryos from an egg-production-selected line (E) did not alter embryonic growth but altered organogenesis. Growth of the F and E lines was altered experimentally in the current study by increasing incubator temperature from 36.8 to 37.2 C during the last 3 d of incubation. Embryonic blood samples were taken and analyzed for glucose, glucagon, IGF-I, and IGF-II concentrations. Increased incubator temperature elevated embryonic plasma glucose concentrations of all treatments compared to controls, which was accompanied by increased plasma glucagon concentration only in the E line embryos. Line and treatment interacted to affect IGF-I and IGF-II concentrations of embryo and hatchlings. Line E embryos increased IGF-I in response to the higher temperature, but controls did not; F embryos altered IGF-II in response to treatment, but controls did not. Alterations in IGF-I in E corresponded to growth responses, whereas IGF-II in F corresponded to metabolic responses. We concluded that changes in turkey embryo growth rates to incubator temperature involved changes in IGF-I. Additionally, IGF-II and glucagon are involved in intermediary metabolism during higher temperature exposure.}, number={7}, journal={POULTRY SCIENCE}, author={Christensen, VL and McMurtry, JP and Donaldson, WE and Nestor, KE}, year={2001}, month={Jul}, pages={949–954} }
 @article{christensen_phelps_2001, title={Injection of thyrotrophin-releasing hormone in turkey embryos elevates plasma thyroxine concentrations}, volume={80}, ISSN={["0032-5791"]}, DOI={10.1093/ps/80.5.643}, abstractNote={The effectiveness of thyrotrophin-releasing-hormone (TRH) as a secretagogue in turkey embryos was tested. Fertilized turkey eggs were injected with TRH after 24 d of incubation. In an experiment to determine an effective route and dose for TRH administration, it was shown that a single manual injection of 200 microL containing 2.15 microg of TRH, into the air cell or the same injection containing 5.0 microg through the bottom of the egg, was effective in elevating plasma concentrations of thyroxine (T4) 60 min after injection. In a second experiment, 5 microg of TRH in a volume of 200 microL was injected through the bottom of each egg. Injections were performed mechanically into eggs held in a commercial incubator. The injection increased blood plasma T4 for 5 h after a 30-min lag. Eggs from two genetic strains of turkeys were injected in Experiment 3. The TRH elicited a persistent response for 120 min from one strain but resulted in a slightly depressed response from the other, suggesting that subtle differences in the maturation of the hypothalamo-hypophyseal-thyroid axis may exist in commercial strains of turkeys. We concluded that TRH is an effective secretagogue for T4 in 24-d-old turkey embryos.}, number={5}, journal={POULTRY SCIENCE}, author={Christensen, VL and Phelps, P}, year={2001}, month={May}, pages={643–646} }
 @article{christensen_davis_2001, title={Maternal dietary iodide influences turkey embryonic thyroid function}, volume={80}, DOI={10.1093/ps/80.9.1286}, abstractNote={Abstract An experiment was designed to examine a mechanism to improve embryonic survival following maternal thyroid hormone manipulation. Commercial turkey breeder hens were fed diets containing supplemental iodide to mimic changes in the maternal thyroid output during an egg production cycle (32 to 48 wk of age). Dietary iodide treatment depressed maternal blood thyroxine (T4) concentrations in a time-dependent manner. Dietary iodide depressed maternal blood 3, 5, 3’-triiodothyronine (T3) levels across all times examined. The maternal dietary treatment increased embryonic blood concentrations of T4 at 25 to 28 d of incubation but depressed blood concentrations of T3 only at 27 d of incubation. In a second trial, the same response was noted in maternal blood when the hens were fed additional iodide with no corresponding effects on T3 concentrations. The iodide treatment decreased embryonic T4 concentrations in the second trial as well but in a time-dependent manner. Iodide accelerated the increase in T4 concentrations coincidental with earlier pipping in eggs from iodide-fed dams compared with controls. The data indicate that the embryonic thyroid function during hatching is dependent upon the maternal thyroid in turkey dams, even though the embryo develops outside the maternal body.}, number={9}, journal={Poultry Science}, author={Christensen, V. L. and Davis, G. S.}, year={2001}, pages={1286–1292} }
 @article{christensen_2001, title={New ideas for egg handling and incubation}, ISBN={0392-0593}, number={7}, journal={Zootecnica International}, author={Christensen, D. V.}, year={2001}, pages={25} }
 @article{crouch_grimes_christensen_garlich_2001, title={Restriction of feed consumption and body weight in turkey breeder hens during the rearing period to improve reproductive performance}, ISBN={0392-0593}, number={5}, journal={Zootecnica International}, author={Crouch, A. N. and Grimes, J. L. and Christensen, V. L. and Garlich, J. D.}, year={2001}, pages={50} }
 @article{christensen_grimes_donaldson_lerner_2000, title={Correlation of body weight with hatchling blood glucose concentration and its relationship to embryonic survival}, volume={79}, ISSN={["1525-3171"]}, DOI={10.1093/ps/79.12.1817}, abstractNote={The negative correlation between selection for rapid growth and embryonic survival was investigated. Embryonic growth was assessed with hatchling weights of a closed population of commercial turkey breeders. Hatchling weights were highly significantly (P < 0.0001) and positively correlated with blood glucose concentrations at hatching. This relationship existed for both tom and hen poults. Significant differences among dams for hatchling blood glucose were observed. Further experiments examined dams selected for producing poults hatching with high (High) or low (Low) blood glucose concentrations. The High embryos were in larger-sized eggs with the same eggshell conductance but with significantly lower conductance constants than the Low embryos, suggesting that Low had longer incubation periods. High embryos grew faster than Low embryos with elevated organ glycogen concentrations. Organic acid analysis indicated elevated plasma alpha-ketoglutarate, urate, and beta-hydroxy butyrate concentrations, suggesting a greater reliance on gluconeogenesis for the High group. Posthatch growth was significantly positively correlated with hatchling blood glucose concentrations in toms but not in hens. Tom poults hatching with elevated glucose were heavier than low glucose hatch mates until 22 wk of age, but hen poults displayed no differences until 16 wk when High hens weighed less than Low hens. These data suggest that the negative correlation between rapid growth and embryonic survival is related to egg-shell conductance constants and embryonic energy metabolism.}, number={12}, journal={POULTRY SCIENCE}, author={Christensen, VL and Grimes, JL and Donaldson, WE and Lerner, S}, year={2000}, month={Dec}, pages={1817–1822} }
 @article{christensen_noble_nestor_2000, title={Influence of selection for increased body weight, egg production, and shank width on the length of the incubation period of turkeys}, volume={79}, ISSN={["0032-5791"]}, DOI={10.1093/ps/79.5.613}, abstractNote={An experiment was designed to study the influence of selection for increased 16-wk BW (F line), egg production (E line), and shank width (FL line) in turkeys on length of the incubation period and to estimate the influence of adult BW (BW50) and egg weight on the incubation period. The base populations for the F, FL, and E lines were randombred control (RBC)2, F, and RBC1, respectively. An additional RBC (RBC3) was also included in the study. The experimental turkey lines differed in length of the incubation period in all trials, indicating genetic differences exist. The E line, in general, had a longer incubation period than the RBC1 line, due to an increase in the time required for external pipping. The FL line had a longer period of incubation than the F line. Differences in the length of the incubation period between the F and RBC2 lines were inconsistent. The F line had a shorter incubation period than the RBC2 line in Trial 1, whereas there was no difference between lines in Trial 2. In Trial 3, the comparison of the F and RBC2 lines was influenced by treatment of the eggs prior to setting. When the eggs were held at room temperature for 29 h prior to setting, the F line had a longer incubation period than the RBC2 line, whereas when the eggs were set directly from the egg cooler, there was no line difference. The line differences in length of the incubation period could not be explained by line differences in egg weight based on a comparison of line means for these traits. Within lines, the regression of length of the incubation period on egg weight was positive and significantly different from zero in three of the six lines. Overall regression of hatching time on egg weight and BW50 was positive for egg weight and negative for BW50. However, only 4% of the variation in the length of the incubation period could be explained by variation in egg weight and BW50. Within lines, the regression coefficient of length of the incubation period on BW50 was not significantly different from zero in any line but the sign was negative in five of six lines.}, number={5}, journal={POULTRY SCIENCE}, author={Christensen, VL and Noble, DO and Nestor, KE}, year={2000}, month={May}, pages={613–618} }
 @article{christensen_grimes_donaldson_lerner_2000, title={Paternal influences on turkey embryonic growth in the absence of changes in egg weight and eggshell conductance}, volume={79}, ISSN={["1525-3171"]}, DOI={10.1093/ps/79.12.1810}, abstractNote={The hypothesis was proposed that embryonic growth could be influenced paternally in the absence of changes in egg weight or eggshell conductance. Sire families were established by selecting 11 sires based on blood sampling of approximately 50 commercial turkey males. Southern blot analysis was used to identify the most distantly related individuals in the subpopulation. Five hen siblings or half-siblings of the males were randomly assigned to each male to randomize effects of egg size and eggshell conductance. Artificial inseminations were performed weekly for 17 wk, using each sire with the assigned hens. Fertilized eggs were collected and set in incubators at biweekly intervals. Offspring were observed at the time of hatching for sex, body weight, and blood glucose concentration. Significant differences among sires were observed at hatching for poult weights and blood glucose concentration, and a significant correlation between the BW and glucose concentration was noted. Progeny of sires with the highest and lowest BW and blood glucose concentrations were subsequently compared. Mean BW of poults from different sires differed by as much as 10 g, although they were hatched from eggs of the same weight. Elevated blood glucose was associated with heavier BW; heavier heart, liver, and muscle weights; a rapid utilization of glycogen at pipping; and increased gluconeogenesis as measured by plasma organic acids and glucose-6-phosphatase activity. We conclude that poult embryonic growth differs even when not mediated by egg size and functional characteristics.}, number={12}, journal={POULTRY SCIENCE}, author={Christensen, VL and Grimes, JL and Donaldson, WE and Lerner, S}, year={2000}, month={Dec}, pages={1810–1816} }
 @article{fairchild_christensen_2000, title={Photostimulation of turkey eggs accelerates hatching times without affecting hatchability, liver or heart growth, or glycogen content}, volume={79}, ISSN={["0032-5791"]}, DOI={10.1093/ps/79.11.1627}, abstractNote={The objective of the current study was to determine the effects of incubating turkey eggs in the presence of incandescent light on hatching times, as well as liver and heart growth and function of the hatched poult. In each of two independent trials, 180 commercial turkey eggs were incubated either in a 12-h incandescent light:dark schedule or continuous darkness throughout the incubation period (n = 360). Hatching time was observed at 8-h intervals following 25 d of incubation. Hatchability was calculated as a percentage of total eggs set, and was also calculated as a percentage of fertilized eggs. Poult weights, blood glucose, liver weights, and heart weights were measured at hatch. Liver and heart glycogen concentrations were analyzed, and comparisons were made of light-treated hatchlings and controls exposed to continuous darkness. The photostimulation of eggs accelerated hatching times (P < or = 0.01) without affecting hatchability or poult weight at hatching. Neither organ weights nor organ glycogen contents of photostimulated poults differed significantly from controls incubated in the dark. Results of this experiment indicate that the incubation length of turkey eggs may be shortened by photostimulation of eggs during the incubation period without significantly affecting embryonic survival, liver or heart growth, or glycogen content.}, number={11}, journal={POULTRY SCIENCE}, author={Fairchild, BD and Christensen, VL}, year={2000}, month={Nov}, pages={1627–1631} }
 @article{christensen_donaldson_nestor_mcmurtry_1999, title={Effect of genetics and maternal dietary iodide supplementation on glycogen content of organs within embryonic turkeys}, volume={78}, ISSN={["1525-3171"]}, DOI={10.1093/ps/78.6.890}, abstractNote={In prior studies it was shown that the growth of turkey embryos was dependent upon maternal dietary iodide as well as genetic selection. The current study posed the question of which organ systems respond to these variables. Embryos from lines selected for 16-wk BW grew at the same rate as unselected embryos from the randombred population serving as the initial source of the selected line until approximately 21 d of incubation (selected = F; randombred control = RBC2). Line differences in growth of F embryos could be accounted for increased liver and heart growth at the expense of muscle growth. Muscle growth increased in the growth-selected line prior to pipping. Muscle growth was affected less when dams were selected for egg production (selected = E; randombred control = RBC1). Muscle growth was slowed in E line embryos compared to that of RBC1, and liver and heart growth were slowed at internal and external pipping stages in E embryos compared to RBC1. Early muscle growth was augmented when F dams were fed supplemental iodide. A similar response was observed in E line embryos but occurred at a later stage of development. Measurements indicated decreased tissue glycogen in liver, heart, and muscle of selected lines may be one possible mechanism by which growth or organ function may come in conflict.}, number={6}, journal={POULTRY SCIENCE}, author={Christensen, VL and Donaldson, WE and Nestor, KE and McMurtry, JP}, year={1999}, month={Jun}, pages={890–898} }
 @article{christensen_donaldson_nestor_mcmurtry_1999, title={Effect of genetics and maternal dietary iodide supplementation on turkey embryonic growth}, volume={78}, ISSN={["1525-3171"]}, DOI={10.1093/ps/78.6.883}, abstractNote={Embryonic growth of a turkey lines selected for 16-wk BW (F) or 180-d egg production (E) was measured and compared to randombred controls (RBC2 or RBC1). Egg weight at setting relative to poult weight at hatching indicated increased growth in F as well as E embryos compared to randombred controls. Eggs from F weighed 10 g more than those of RBC2 (P < or = 0.0001) but the poults at hatching were only 8 g heavier (P < or = 0.0001). Water vapor loss during incubation indicated that only 0.9% of the difference could be accounted for by water vapor loss. Selection for increased 16-wk BW resulted in decreased embryo growth rates relative to hatchling mass (P < or = 0.0001) beginning at Day 16 of incubation compared to that of RBC2. Eggs from E weighed 15 g less than RBC1 (P < or = 0.0001) but produced poults weighing only 7 g less (P < or = 0.0001). Incubation water vapor loss was depressed in E compared to RBC1 (P < or = 0.0001) but accounted for only 1.4% of the difference between hatchling weights. Selection for egg production increased embryo growth rates (relative to hatchling mass) measured at 4-d intervals compared to those of the RBC1 line (P < or = 0.05). Iodide supplementation of the maternal diet depressed (P < or = 0.05) glycogen in F embryos but interacted with line to generally increase glycogen in E embryos. Increased glycogen was related to increased growth rates in E but not F line embryos. It may be concluded that iodide supplementation of the material diet and genetics are determinants of embryonic growth in turkeys.}, number={6}, journal={POULTRY SCIENCE}, author={Christensen, VL and Donaldson, WE and Nestor, KE and McMurtry, JP}, year={1999}, month={Jun}, pages={883–889} }
 @article{christensen_donaldson_nestor_1999, title={Effect of supplemental oxygen on blood plasma organic acids within embryos from selected lines of turkeys}, volume={78}, ISSN={["0032-5791"]}, DOI={10.1093/ps/78.11.1601}, abstractNote={The hypothesis was tested that increased oxygen tensions during the plateau stage of oxygen consumption (25 and 26 d of incubation) would cause different metabolic responses from embryos selected for increased egg production or growth. Embryos were exposed to 171 or 152 mm Hg partial pressure of oxygen from 25 to 28 d of incubation, a time when the oxygen conductance properties of the eggshell are exceeded by the embryonic tissue demands for oxygen. Carbohydrate and lipid metabolism were observed by measuring plasma organic acids in embryos from selected lines and randombred controls. (E was selected for increased egg production; RBC1 is the randombred line from which it was selected. F was selected for increased BW; RBC2 is the randombred line from which it was selected.) During the plateau stage in oxygen consumption, RBC2 embryos responded to added oxygen by utilizing fat rather than carbohydrate, whereas F embryos responded by using less fat as well as less carbohydrate from the liver and kidney. The response of F embryos to added oxygen is the opposite that might be expected for aerobic metabolism. The reason that selection for growth has resulted in such a metabolism is unknown. The E embryos displayed depressed lactate and beta-hydroxybutyrate levels, but plasma urates were elevated compared with RBC1, suggesting that the selection for egg production has also resulted in a unique metabolism. The embryonic processes described in the current study suggest that selected embryos are unable to respond to elevated partial pressure of oxygen by adjusting energy metabolism, which may result in increased embryonic mortality during this stage.}, number={11}, journal={POULTRY SCIENCE}, author={Christensen, VL and Donaldson, WE and Nestor, KE}, year={1999}, month={Nov}, pages={1601–1605} }
 @article{coles_croom_brake_daniel_christensen_phelps_gore_taylor_1999, title={In ovo peptide YY administration improves growth and feed conversion ratios in week-old broiler chicks}, volume={78}, ISSN={["0032-5791"]}, DOI={10.1093/ps/78.9.1320}, abstractNote={The effects of in ovo Peptide YY (PYY) administration on growth and feed conversion ratios in a commercial broiler line were investigated. Six hundred Ross male x Cobb female eggs were administered either 0.9% saline (control) or 600 microg/kg egg weight PYY in ovo at Day 18 of incubation. On day of hatching, 210 birds from each treatment group were randomly placed by sex into pens. Body weights at placement were not different between treatment groups. Average chick body weight and adjusted pen feed conversion ratios were improved by PYY in ovo treatment at 7 d posthatch (165.7 vs. 170.2 g, P<0.02; and 1.55 vs. 1.49, P<0.04, respectively). No significant differences between treatments were noted for these parameters at 21 or 42 d of age. These results suggest that in ovo treatment of broiler chicken eggs with gastrointestinal hormones that increase intestinal nutrient absorption, such as PYY, may enhance chick performance.}, number={9}, journal={POULTRY SCIENCE}, author={Coles, BA and Croom, WJ and Brake, J and Daniel, LR and Christensen, VL and Phelps, CP and Gore, A and Taylor, IL}, year={1999}, month={Sep}, pages={1320–1322} }
 @article{caldwell_johnson_yule_grimes_ficken_christensen_1999, title={Increased egg production in juvenile turkey hens after active immunization with vasoactive intestinal peptide}, volume={78}, DOI={10.1093/ps/78.6.899}, abstractNote={Juvenile turkey hens were actively immunized against vasoactive intestinal peptide (VIP) prior to photostimulation to evaluate its effect on enhancing egg production. VIP antibody titers were generated in the VIP immunized hens and a greater rate of egg production per hen was observed compared to controls. In addition, the first egg laying cycle was extended for an additional 7 wk without a significant decline in egg production. Over a 27-wk period, 116 settable eggs per hen were produced from the VIP immunized hens as compared to 102 and 90 eggs for the keyhole limpet hemocyanin and saline control groups, respectively. Based on the increased egg production and the extension of the first egg laying cycle, this experiment demonstrates that VIP immunization of turkey hens is potentially economically relevant.}, number={6}, journal={Poultry Science}, author={Caldwell, S. R. and Johnson, A. F. and Yule, T. D. and Grimes, J. L. and Ficken, M. and Christensen, V. L.}, year={1999}, pages={899–901} }
 @article{croom_brake_coles_havenstein_christensen_mcbride_peebles_taylor_1999, title={Is intestinal absorption capacity rate-limiting for performance in poultry?}, volume={8}, ISSN={["1537-0437"]}, DOI={10.1093/japr/8.2.242}, abstractNote={Abstract In recent years, there has been a growing perception that limitations in gastrointestinal absorption may be detrimental to posthatch survival and subsequent performance. This perception is based on a large body of information demonstrating that genetic selection for growth in domestic poultry alters intestinal structure from that of their wild counterparts. Furthermore, recent advances in our understanding of the energetic costs of absorption suggest that biochemical as well as structural changes in intestinal function have decreased absorptive function and efficiency in both chickens and turkeys. The recent discovery that some gastrointestinal peptides enhance nutrient absorption has allowed limited, direct testing of this hypothesis. The results of preliminary studies indicate that intestinal absorption enhancement technology may have beneficial practical application. More detailed studies are needed to fully assess the economic potential of intestinal absorption enhancement in poultry.}, number={2}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Croom, WJ and Brake, J and Coles, BA and Havenstein, GB and Christensen, VL and McBride, BW and Peebles, ED and Taylor, IL}, year={1999}, pages={242–252} }
 @article{christensen_donaldson_nestor_1999, title={Length of the plateau and pipping stages of incubation affects the physiology and survival of turkeys}, volume={40}, ISSN={["1466-1799"]}, DOI={10.1080/00071669987737}, abstractNote={1. The hypothesis tested was that accelerating the rate at which a turkey embryo passes through the Plateau and Pipping stages (incubation days 25 to 28) affects growth and embryonic mortality. 2. Eggs from 4 genetic lines were incubated similarly until 24 d of incubation. The eggs were divided at random, half incubated at 36.8 degrees C (CON) and the remaining half incubated at 37.3 degrees C (FAST). 3. The passage time for each developmental stage was recorded at 4 h intervals. Tissues were collected and measured for growth, and glycogen concentration at each developmental stage in response to the accelerated development. 4. The FAST treatment accelerated passage through the Plateau in some lines but not others, but time to pip was shortened in all genetic lines. Embryonic survival rate was affected differently by FAST. Slower growth in response to FAST enhanced survival. 5. In conclusion the rate at which genetically different embryos grow, mature and survive may involve choices among the 3 processes.}, number={2}, journal={BRITISH POULTRY SCIENCE}, author={Christensen, VL and Donaldson, WE and Nestor, KE}, year={1999}, month={May}, pages={297–303} }
 @article{crouch_grimes_christensen_garlich_1999, title={Restriction of feed consumption and body weight in two strains of large white turkey breeder hens}, volume={78}, ISSN={["0032-5791"]}, DOI={10.1093/ps/78.8.1102}, abstractNote={Large White female-line turkey breeder hen poults (576) of two strains (N, female line and B, male line) were brooded by strain in floor pens from day of hatch until 3 wk of age (WOA). At 3 WOA, all poults were randomly distributed by strain to 48 floor pens in a curtain-sided house. Poults were feed (calorie) restricted beginning at 3 (N3, B3) or 6 (N6, B6) WOA to obtain a 45% reduction in BW at 16 WOA compared to ad libitum controls (NC, BC). At 16 WOA, all hens were gradually returned to ad libitum feeding. At 18 to 30 WOA, all hens were subjected to 8 h light/d. At 30 WOA, all hens were photostimulated with 15.5 h/d. Hens were inseminated weekly with semen from same strain, male-line breeder males. Eggs were collected daily, and all settable eggs from weeks of lay (WOL) 5 to 6, 10 to 11, 15 to 16, 20 to 21, and 24 to 25 were incubated by pen in a common incubator for each set date. Measurements included BW, feed consumption, egg production, mortality, egg fertility, egg hatchability, and poult weight. Statistical analysis of means was performed by strain. Target BW were obtained for feed-restricted hens. Restricted hens increased their feed consumption upon re-alimentation but did not achieve the cumulative feed consumption or BW of control fed hens by 56 WOA. Egg production of N3 hens was greater than NC hens for WOL 2 and 3. Total and settable eggs per hen were greater for N3 hens than for NC for WOL 1 to 5. There were no differences observed for egg weight, egg fertility, hatch of all eggs set, hatch of fertile eggs, or offspring weight among N hen treatments. The B0 hens produced more eggs than B3 or B6 hens. The B6 hens produced lighter weight eggs than B0 hens. It was concluded that early severe feed restriction of female line breeder hens might improve subsequent reproductive performance.}, number={8}, journal={POULTRY SCIENCE}, author={Crouch, AN and Grimes, JL and Christensen, VL and Garlich, JD}, year={1999}, month={Aug}, pages={1102–1109} }
 @article{christensen_mcmurtry_donaldson_nestor_1999, title={Supplemental oxygen affects plasma insulin-like growth factors in embryos from selected lines of turkeys}, volume={78}, ISSN={["1525-3171"]}, DOI={10.1093/ps/78.11.1606}, abstractNote={Recent advances in our understanding of insulin-like growth factors (IGF) have improved our knowledge of the physiological roles of these peptide hormones during avian embryogenesis. However, little is known about changes in plasma IGF in response to changes in environmental factors. The objective of the studies reported herein was to examine the response of IGF-I and IGF-II in turkey embryos to changes in incubator gaseous conditions. Two experiments were conducted in which the fractional percentage of oxygen in the incubation atmosphere, a factor known to influence the energy metabolism of embryos, was investigated for its effects on circulating IGF-I and IGF-II in developing turkey embryos. Oxygenation during pipping and hatching is known to depress lactate, urates, and beta-hydroxybutyrate in growth-selected poult embryos, but elevate them in randombred control poult embryos. Plasma concentrations of IGF-II were similarly depressed in the growth-selected hatchlings. Circulating growth factor concentrations were influenced by oxygenation in lines of turkeys in which greater oxygen concentrations enhanced cardiac growth. Enhanced cardiac growth was inversely related to IGF-I concentrations in those genetic lines of turkeys. It was concluded that changes in poult embryo energy balance as well as changes in growth to adapt to environmental incubator conditions may involve changes in IGF-I and IGF-II. These changes appeared dependent on the genetics of embryos; embryos selected for growth show more fluctuation in response to environmental oxygen than embryos selected for egg production.}, number={11}, journal={POULTRY SCIENCE}, author={Christensen, VL and McMurtry, JP and Donaldson, WE and Nestor, KE}, year={1999}, month={Nov}, pages={1606–1610} }
 @article{fan_croom_christensen_bird_daniel_mcbride_eisen_1998, title={Apparent energetic efficiency of jejunal glucose uptake in young adult turkeys selected for rapid growth}, volume={78}, ISSN={["0008-3984"]}, DOI={10.4141/A97-099}, abstractNote={ A rapid growth line (F) and a randombred control line (RBC2) of 16-wk-old unsexed turkeys were used to examine the effect of genetic selection for rapid growth on jejunal O2 consumption, glucose uptake and apparent energetic efficiency of glucose uptake. F line had 85% greater feed-deprived body weight (FBW, kilogram) than RBC2 line (P < 0.001) at 16 wk of age and a lighter (gram/kilogram FBW) and shorter (centimeter/kilogram FBW) small intestine and jejunum (P < 0.001). Additionally, the jejunum was composed of a higher proportion (P < 0.007) of mucosal tissue. There was no difference between the lines in apparent energetic efficiency (nmoles ATP expended/nmoles glucose uptake) of jejunal active glucose uptake. These data suggest selection for rapid growth in turkeys does not result in more efficient glucose uptake from the jejunum. Key words: Genetic selection, small intestine, glucose uptake, respiration, turkey }, number={3}, journal={CANADIAN JOURNAL OF ANIMAL SCIENCE}, author={Fan, YK and Croom, WJ and Christensen, VL and Bird, AR and Daniel, LR and McBride, BW and Eisen, EJ}, year={1998}, month={Sep}, pages={301–306} }
 @article{temple_weiss_walker_barnes_christensen_miyamoto_shelton_orndorff_1998, title={Bordetella avium virulence measured in vivo and in vitro}, volume={66}, number={11}, journal={Infection and Immunity}, author={Temple, L. M. and Weiss, A. A. and Walker, K. E. and Barnes, H. J. and Christensen, V. L. and Miyamoto, D. M. and Shelton, C. B. and Orndorff, P. E.}, year={1998}, pages={5244–5251} }
 @article{grimes_christensen_whittaker_1997, title={Filtering and the viability of turkey spermatozoa}, volume={6}, ISSN={["1056-6171"]}, DOI={10.1093/japr/6.1.34}, abstractNote={Abstract The efficacy of turkey semen filtration was tested in six trials utilizing 63, 90, or 180 μm (M2, M3, CF) filters. Nonfiltered semen was compared to filtered semen using the modified ethidium bromide test for fresh and 24-hr stored semen in control buffer (100%) and stress buffer (20%) for all six trials. In the first four trials, filtered semen sometimes had higher sperm viability (P}, number={1}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Grimes, JL and Christensen, VL and Whittaker, R}, year={1997}, pages={34–38} }
 @article{queen_christensen_may_1997, title={Supplemental thyroid hormones and molting in turkey breeder hens}, volume={76}, ISSN={["1525-3171"]}, DOI={10.1093/ps/76.6.887}, abstractNote={The objective of the current study was to determine whether thyroid physiology may affect molting time in turkeys. Two trials using approximately 144 hens were conducted to elucidate thyroidal factors that limit the molting process. Thyroid hormones or a thyroid blocker (thiouracil) were given to the hens during a molt by supplementing the diet with thyroxine (T4), triiodothyronine (T3), or thiouracil. Supplementing with T4 reduced the number of days to return to egg production, whereas supplementing with thiouracil or T3 prolonged days to first egg. The observations support previous suggestions of separate functions for T3 and T4 during molting. As had been observed many times previously, the feeding of thiouracil delayed the molt but did not completely stop the molting process. The hens fed thiouracil returned to 50% egg production nearly 10 d after the control group, whereas T3 prolonged the return to 50% egg production nearly 1 wk later. The data indicate the endogenous low levels of T4, but not T3 in modern strains of turkeys may contribute to a relatively longer molting period of turkey breeder hens induced to molt out of season.}, number={6}, journal={POULTRY SCIENCE}, author={Queen, WH and Christensen, VL and May, JD}, year={1997}, month={Jun}, pages={887–893} }
 @article{christensen_davis_lucore_1996, title={Eggshell conductance and other functional qualities of ostrich eggs}, volume={75}, ISSN={["1525-3171"]}, DOI={10.3382/ps.0751404}, abstractNote={Eggshell conductance was measured and eggshell conductance constants were calculated for eggs from ostriches. In addition, egg water, yolk, albumen, shell, and total solids were measured in an effort to determine the maternal investment of ostrich eggs. The results of the study suggest that the optimal incubator humidity for ostrich eggs is less than 25% to allow a 15% loss of initial egg mass during the 45-d incubation period. This low humidity does not preclude increasing humidity during the actual hatching process. In addition, incubation temperatures need to be adjusted to allow a longer development time for the embryo to attain an adequate level of maturity to survive the plateau stage in oxygen consumption or to prevent the use of limited energy of the yolk to survive the anoxia of tucking and internal pipping. The optimal incubation temperature of ostrich eggs appears to be between 36.1 and 36.9 C.}, number={11}, journal={POULTRY SCIENCE}, author={Christensen, VL and Davis, GS and Lucore, LA}, year={1996}, month={Nov}, pages={1404–1410} }
 @article{christensen_1996, title={Embryonic turkey respiration important to hatch and quality}, volume={55}, number={9}, journal={Poultry Digest}, author={Christensen, V. L.}, year={1996}, pages={21} }
 @article{christensen_donaldson_mcmurtry_1996, title={Physiological differences in late embryos from turkey breeders at different ages}, volume={75}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0750172}, abstractNote={Physiological mechanisms were measured in embryos from turkey hens of different ages to determine associations with declines in hatchability as breeder hens age. As the hens aged from 32 to 54 wk of age, embryonic viability declined (P < 0.05). The greatest proportional increase (P < 0.01) in embryonic mortality of aging hens occurred at the plateau stage in oxygen consumption or immediately thereafter at pipping. Eggshell conductance constants increased (P < 0.01) as hens aged but did not change after mid-lay, suggesting an alteration in respiration for the embryos in eggs produced by older hens compared to eggs produced by the same hens at younger ages. The alteration may cause embryos in eggs from older hens to reach the plateau stage in oxygen consumption (approximately 25 to 26 d of incubation) earlier in development than embryos from young hens. Hepatic and cardiac glycogen concentrations were greatest (P < 0.001) in embryos from hens at the youngest age and then declined (P < 0.05) as the hens aged. Embryonic blood plasma glucose concentrations declined (P <0.05) similarly. Plasma thyroxine (T4) and triiodothyronine (T3) concentrations were measured in embryos from the hens at different ages as well. Increased (P < 0.05) T4 was evidenced in embryos from the youngest hens, whereas increased (P < 0.05) T3 activity was evident in embryos from hens of older ages. It was concluded that the decline in hatchability seen as turkey breeder hens age may have a basis in the differences seen in the physiology of hatching in embryos. Specifically, thyroid influences on growth and carbohydrate metabolism may be involved in decreased embryonic viability.}, number={2}, journal={POULTRY SCIENCE}, author={Christensen, VL and Donaldson, WE and McMurtry, JP}, year={1996}, month={Feb}, pages={172–178} }
 @article{christensen_havenstein_davis_1995, title={EGG CHARACTERISTICS, CARBOHYDRATE-METABOLISM, AND THYROID-HORMONES IN LATE CHICK-EMBRYOS FROM DIFFERENT GENETIC LINES}, volume={74}, ISSN={["1525-3171"]}, DOI={10.3382/ps.0740551}, abstractNote={Functional eggshell qualities, thyroid hormones, and carbohydrate metabolism of chick embryos at the end of incubation were compared between a modern (Arbor Acres line) and a randombred control population (Athens-Canadian Randombred). Embryos from the Arbor Acres genetic line developed in larger eggs with more albumen and less yolk than Athens Canadian Randombred lines. Percentage shell and functional eggshell properties measured as eggshell conductance constants did not differ between genetic lines. On a relative basis, hearts were generally smaller and livers heavier in Arbor Acres than in Athens-Canadian Randombred birds. Heart and liver glycogen concentrations were greater in Athens-Canadian Randombred than in Arbor Acres embryos. However, blood glucose was greater in Randombred than in Arbor Acres embryos only at internal pipping, a time of hypoxia and hypercapnia. Blood plasma concentrations of thyroxine did not differ significantly between the modern and Randombred embryos at any stage examined. Modern broiler chick embryos possessed greater concentrations of triiodothyronine as well as greater triiodothyronine to thyroxine ratios than Randombred embryos at external pipping and hatching. It can be inferred from the data that chick embryos differ in their use of carbohydrate during late development between modern and Randombred genetic lines.}, number={3}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and HAVENSTEIN, GB and DAVIS, GS}, year={1995}, month={Mar}, pages={551–562} }
 @article{christensen_1995, title={Factors affecting hatchability of turkey embryos}, volume={6}, number={1}, journal={Poultry and Avian Biology Reviews}, author={Christensen, V. L.}, year={1995}, pages={71} }
 @article{christensen_nestor_1994, title={CHANGES IN FUNCTIONAL QUALITIES OF TURKEY EGGSHELLS IN STRAINS SELECTED FOR INCREASED EGG-PRODUCTION OR GROWTH}, volume={73}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0731458}, abstractNote={Much past research has been devoted to physical eggshell qualities, i.e., weight, deformation, or egg density, but little research has investigated the functional eggshell qualities when expressed in terms of eggshell conductance to gases. Conductance is a measure of the ease with which gases diffuse across the pores of the shell and is (by Fick's law) determined by the number and geometry of the individual pores. The objective of the present study was to determine changes that have occurred in functional eggshell characteristics (eggshell conductance) following selection for egg production or growth over nearly 30 generations. Major changes have occurred in the physical dimensions of eggs from selected lines of turkeys compared with their respective randombred controls. Egg weights increased 11% due to selection for growth and decreased 14% due to selection for egg production. Other measurements such as length and width increased allometrically with egg weights. Selection for egg production has decreased the physical dimensions (egg weight, volume, or surface area) of eggs, and selection for growth has increased the same measurements, but adjustments have not been made by selected hens to increase or decrease the functional characteristic (conductance) allometrically (conductance constants). An interaction was observed in eggshell conductance constants as the hens aged, suggesting that genetic selection may affect functional characteristics. This suggests that the energetics of embryonic development may be different in eggs from turkey hens of various ages. Energetics may result in poor hatchability and poult quality. It can be concluded that as the hens aged the conductance and conductance constants did not change allometrically with increasing egg weight.(ABSTRACT TRUNCATED AT 250 WORDS)}, number={9}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and NESTOR, KE}, year={1994}, month={Sep}, pages={1458–1464} }
 @article{christensen_donaldson_1994, title={EFFECTS OF THE MATERNAL THYROID STATUS ON EMBRYO PHYSIOLOGY AND HATCHABILITY OF COMMERCIAL TURKEY EGGS}, volume={73}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0730236}, abstractNote={Fertile turkey eggs produced by commercial hens fed iodine or triiodothyronine were compared with those from hens fed a control diet to observe the effects of the maternal thyroid status on the energy budget of turkey eggs. Dietary iodine improved hatchability, decreased the number of dead pips, and maintained blood glucose concentrations during pipping and hatching with less reliance on hepatic gluconeogenesis (as assessed by glucose-6-phosphatase activity) compared with controls. Hatchability of eggs from hens fed triiodothyronine was not different from that of control hens but was less than those of iodine-fed hens. The data suggest that the maternal thyroid function of commercial breeder hens can influence hatchability of their eggs and that dietary iodine may be a means to improve hatchability of commercial turkey eggs.}, number={2}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and DONALDSON, WE}, year={1994}, month={Feb}, pages={236–244} }
 @article{christensen_donaldson_nestor_1993, title={EFFECT OF MATERNAL DIETARY TRIIODOTHYRONINE ON EMBRYONIC PHYSIOLOGY OF TURKEYS}, volume={72}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0722316}, abstractNote={The objective of the present experiment was to feed triiodothyronine (T3) to lines of turkey breeders selected for egg production and growth, and an unselected control line. The data were collected to determine a genetic basis for thyroid-mediated maternal effects on embryonic physiology and livability. At 30 wk of age, turkeys of the three lines were photostimulated and half of each line was fed a diet containing .5 ppm T3. Maternal dietary T3 increased egg weight, reduced yolk solids and eggshell conductance constants, and increased albumen solids and water in eggs in all lines compared with control eggs. Hatchability in all lines was not affected by the dietary treatment (Control = 72.2%; T3 treatment = 70.7%), but there was a significant interaction between dietary T3 and line of turkey for the time of embryonic mortality, time of hatching, and carbohydrate metabolism of the embryo. The T3 increased mortality of the Egg line and unselected line during pipping, increased mortality of the Growth line in the plateau stage, but decreased its mortality during internal pipping. Reduced glycogen in liver as well as a reduced gluconeogenesis were evident in embryos of the two selected lines fed T3. It is concluded that genetic lines may have different metabolic patterns based on their genetic constitution in order to compensate for variations in egg solids and eggshell conductance constants. The metabolic patterns are reflected in different levels of embryonic blood plasma glucose, glycogen, and gluconeogenesis.}, number={12}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and DONALDSON, WE and NESTOR, KE}, year={1993}, month={Dec}, pages={2316–2327} }
 @article{christensen_donaldson_nestor_1993, title={EMBRYONIC VIABILITY AND METABOLISM IN TURKEY LINES SELECTED FOR EGG-PRODUCTION OR GROWTH}, volume={72}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0720829}, abstractNote={Abstract Lines of turkeys selected genetically for rapid growth or egg production and their respective randombred control populations were examined for physiological factors influencing their hatchability. Hatchability of fertile eggs was improved (P ≤ .05) in the growth line but not in the egg production line when compared with randombred control populations. Embryonic mortality of both selected lines was lower during the 1st wk of incubation but higher during pipping than that observed for the mortality of the randombred control embryos. Eggshell conductance constants were lower (P ≤ .05) in genetically selected lines compared with constants for eggs of the randombred control strains, which suggests that embryos from selected lines have less access to oxygen. Thus, genetic selection regardless of whether for growth or egg production reduced oxygen consumption during external pipping and for hatched poults, so the reduction cannot be attributed specifically to growth or egg production. Metabolic rate as measured by oxygen consumption during external pipping and posthatch was reduced (P ≤ .05) in the embryos of the selected lines compared with controls. Thus, oxygen availability through eggshells prior to pipping may be vital in determining survival rates of late embryos. Lower oxygen consumption would cause embryos to rely more on stored glycogen for energy during pipping. Hepatic and cardiac glycogen stores and blood plasma glucose concentrations indicated the embryos of growth and egg production lines had less (P ≤ .05) stored glycogen than control embryos. The data suggest that there may be a relationship between carbohydrate accrual prior to pipping, its utilization during pipping, and subsequent embryonic survival during pipping and hatching among the lines and that these differences may be associated with the genetics of growth or egg production.}, number={5}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and DONALDSON, WE and NESTOR, KE}, year={1993}, month={May}, pages={829–838} }
 @article{christensen_1993, title={The influence of incubation on hatchability and poult quality}, volume={16}, number={5}, journal={Zootecnica International}, author={Christensen, U. L.}, year={1993}, pages={46} }
 @article{christensen_donaldson_1992, title={Effect of oxygen and maternal dietary iodine on embryonic carbohydrate metabolism and hatchability of turkey eggs}, volume={71}, DOI={10.3382/ps.0710747}, abstractNote={Fertile turkey eggs were produced by hens fed supplemental iodine to decrease eggshell conductance. The eggs were then incubated in an oxygen-enriched environment during Days 25 and 26 of incubation to test the hypothesis that maternal dietary iodine has separate effects on the eggshell permeability and the developing embryo. Oxygen supplementation improved hatchability regardless of dietary iodine treatment, suggesting that oxygen availability may limit hatching of eggs with normal gas conductance. Oxygen and dietary iodine did not affect body weight but interacted prior to pipping to affect embryonic liver and heart glycogen. Dietary iodine increased liver glycogen at internal pipping. The effects of oxygen on embryos, which were correlated directly with hatchability, were increased liver growth prior to pipping and increased heart weight at external pipping and posthatching. It was concluded that supplementing oxygen to incubating turkey eggs may improve hatchability by increasing liver and heart growth. Dietary iodine played only a minor or modulating role in assisting embryos to survive.}, number={4}, journal={Poultry Science}, author={Christensen, V. L. and Donaldson, W. E.}, year={1992}, pages={747} }
 @article{christensen_donaldson_1992, title={THE IMPORTANCE OF TIMELY REMOVAL FROM THE INCUBATOR OF HATCHED POULTS FROM 3 COMMERCIAL STRAINS}, volume={71}, ISSN={["1525-3171"]}, DOI={10.3382/ps.0711823}, abstractNote={Abstract Egg size and functional qualities differ among strains of commercial turkeys. Thus, energy budgets of egg contents and eggshell conductance constants may represent different strategies for hatching and more energy may be expended by some strains than others. The objective of the present study was to determine the effects on poult quality of holding hatchling poults in the incubator for 12 or 24 h posthatching. Eggs from three strains of commercial turkey breeder hens were obtained from a commercial turkey breeding company, numbered, randomly distributed, and set in incubators. The time of hatching of each egg was observed at 4-h intervals and a random sample of hatchlings emerging from the shell at 648 and 660 h of incubation was compared with poults kept in the incubator until 672 h of incubation. Holding poults in incubators 12 or 24 h posthatching reduced (P ≤ .05) total body weight of all strains examined but increased (P ≤ .05) relative heart and liver weights. Holding time interacted (P ≤ .05) with strain of turkey to increase blood plasma glucose and decrease heart glycogen. Holding decreased (P ≤ .001) liver glycogen precipitously in all three strains. It was concluded that holding poults in incubators 12 or 24 h posthatching has detrimental effects on carbohydrate metabolism and some strains of turkeys respond to the holding time better than others. Therefore, poult quality of commercial turkey strains may be affected differently by keeping them in the incubator posthatching.}, number={11}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and DONALDSON, WE}, year={1992}, month={Nov}, pages={1823–1829} }
 @article{christensen_donaldson_ort_grimes_1991, title={INFLUENCE OF DIET-MEDIATED MATERNAL THYROID ALTERATIONS ON HATCHABILITY AND METABOLISM OF TURKEY EMBRYOS}, volume={70}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0701594}, abstractNote={Large White turkey breeder hens from a strain exhibiting poor hatchability were fed thyroid-altering diets. The following dietary treatments were fed to randomized groups of hens for 15 wk of egg laying: 1) 16.5% protein turkey breeder diet (control), 2) the control diet containing 2.1 ppm supplemental iodine, 3) the control diet containing .1% thiouracil, and 4) the control diet containing .5 ppm triiodothyronine (T3). Blood samples were taken from hatching embryos from hens fed each diet. Embryonic hearts and livers were weighted prior to and during pipping as well as after hatching. Blood plasma was analyzed for thyroxine (T4), T3, and glucose. Livers were assayed for glucose-6-phosphatase activity. Supplemental maternal dietary iodine elevated embryonic T4 concentrations prior to pipping. Dietary T3 and iodine increased hepatic glucose-6-phosphatase activity and blood plasma glucose concentration prior to pipping. Feeding thiouracil increased embryonic liver weights but decreased heart and body weights. Blood plasma T4 was elevated in embryos from hens fed thiouracil but blood glucose levels were depressed because of a lack of increased glucose-6-phosphatase activity. Feeding iodine decreased the enzyme activity at internal pipping. It is suggested from the data that maternal thyroid metabolism may influence hatchability via embryonic thyroid and carbohydrate metabolism during hatching.}, number={7}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and DONALDSON, WE and ORT, JF and GRIMES, JL}, year={1991}, month={Jul}, pages={1594–1601} }
 @article{christensen_ort_1991, title={IODINE TOXICITY IN LARGE WHITE TURKEY BREEDER HENS}, volume={70}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0702402}, abstractNote={Iodine was fed to turkey breeder hens during a 20-wk laying cycle to determine the appropriate dietary level to support reproduction and avoid toxicity. A basal diet that contained by analysis. 7 ppm iodine supported good hatchability of Large White turkey eggs. Supplementing 35 or 350 ppm iodine to the basal diet resulted in toxic effects (P less than or equal to .05) on hatchability. Feeding 350 ppm also depressed (P less than or equal to .05) egg weights, egg production, and eggshell water vapor conductance. Embryonic mortality data indicated that toxic effects of iodine on embryos occur principally during the 1st wk of incubation and immediately prior to and during pipping. It was concluded that iodine toxicity may occur in Large White turkey breeder hens when 350 ppm are fed in the diet.}, number={12}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and ORT, JF}, year={1991}, month={Dec}, pages={2402–2410} }
 @article{christensen_donaldson_ort_1991, title={THE EFFECT OF DIETARY IODINE ON THE HATCHABILITY OF EGGS FROM 2 COMMERCIAL STRAINS OF TURKEYS}, volume={70}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0702529}, abstractNote={Supplemental dietary iodine (3.5 mg/kg) was fed to two commercial strains [British United Turkeys (B) and Nicholas (N)] of turkey breeder hens. The basal diet contained .7 mg/kg of iodine. Observations were made on hen body weights, feed consumption, hatchability, egg weights, and egg functional characteristics to test the hypothesis that there are differences between commercial strains of turkey breeder hens in the dietary iodine requirement for reproductive success. Supplemental iodine decreased (P less than or equal to .05) functional egg characteristics of both strains. Egg production and hatchability were influenced by an interaction between strains and dietary iodine (P less than or equal to .05). In Strain B hens, egg production and hatchability declined (P less than or equal to .05) when hens were fed supplemental iodine but in Strain N hens no effects on hatchability were observed and egg production increased (P less than .05) with iodine supplementation. The decline in hatchability of eggs from Strain B hens was due to significant (P less than or equal to .05) increases in embryonic mortality during the 1st wk of incubation and during pipping. The treatments resulting in depressed hatchability caused embryos to rely more (P less than or equal to .05) on glycogenolysis than gluconeogenesis during pipping and hatching. The Strain B embryos utilized gluconeogenesis more during pipping (P less than or equal to .05) than Strain N embryos and embryos from Strain B iodine-fed hens had a lower rate of gluconeogenesis than those from hens not fed iodine. It is concluded that there are differences among strains of turkey breeder hens in their dietary iodine requirement for optimal hatchability.}, number={12}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and DONALDSON, WE and ORT, JF}, year={1991}, month={Dec}, pages={2529–2537} }
 @article{christensen_ort_1990, title={INFLUENCE OF DIET-MEDIATED MATERNAL THYROID ALTERATIONS ON FUNCTIONAL-PROPERTIES OF TURKEY EGGS}, volume={69}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0691576}, abstractNote={Maternal thyroid status was altered by means of diet to determine its effect on functional properties of turkey eggshells. Hens were fed a control diet (CON), the CON diet containing .5 ppm triiodothyronine (T3), the CON diet containing 2.1 ppm iodine as potassium iodide (KI) or the CON diet containing .1% thiouracil (THIO). Feeding T3 decreased plasma thyroxine but elevated plasma T3 concentrations compared to CON. The KI diet had no effect on plasma thyroid hormone concentrations, but feeding THIO depressed plasma thyroxine with no effect on T3, resulting in an elevated ratio of the two hormones compared to the CON ratio. Feeding KI decreased egg volume and T3 increased egg density compared to CON, but no effects on egg weight, surface area, width, or length were noted. Dietary T3 depressed eggshell water vapor conductance compared to CON. Dietary iodine resulted in thinner eggshells with fewer pores than the CON, whereas THIO caused significantly more pores in eggshells than CON but had no effects on shell thickness. Dietary KI had no effects on maternal plasma thyroid hormone concentrations, suggesting that the effects were due to iodine availability rather than to thyroid hormones. It is concluded that the availability of iodine to turkey breeder hens may influence eggshell characteristics.}, number={9}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and ORT, JF}, year={1990}, month={Sep}, pages={1576–1581} }
 @article{christensen_1990, title={Sperm competition and fertilization in turkeys}, number={54}, journal={Les Colloques de l'INRA}, author={Christensen, V. L.}, year={1990}, pages={91} }
 @article{christensen_1990, title={THE MINERAL CONCENTRATION CHANGE OF TURKEY EGGSHELL MEMBRANES DURING INCUBATION}, volume={69}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0690992}, abstractNote={Abstract Membranes from fertile and infertile turkey eggs were examined during incubation to determine the content of Ca, Mg, Na, and K. The Ca concentration in shell membranes of fertile eggs increased (P≤.05) as compared with that in infertile eggs, but concentrations of Mg, Na, and K in shell membranes of fertile eggs declined (P≤.05) as compared with those in infertile eggshell membranes. The data suggest a possible role for some minerals in regulating functional eggshell properties.}, number={6}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL}, year={1990}, month={Jun}, pages={992–998} }
 @article{christensen_bagley_1989, title={EFFICACY OF FERTILIZATION IN ARTIFICIALLY INSEMINATED TURKEY HENS}, volume={68}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0680724}, abstractNote={Research was conducted to develop an artificial insemination protocol optimizing the use of spermatozoa by turkey breeder hens. Large White turkey hens were inseminated on Days 14 and 17 postphotostimulation with 200 million spermatozoa from one male phenotype to fill the oviductal storage sites. Artificial inseminations were then performed weekly for 20 wk with different spermatozoa numbers of another male phenotype. Fertility and phenotype of each poult were determined at hatch to ascertain which insemination, initial or subsequent, was responsible for fertility. Inseminating weekly with 200 million viable spermatozoa cells resulted in better fertility but did not optimize the hen's utilization of spermatozoa from the initial inseminations. When fewer spermatozoa were inseminated weekly (50 million cells), more progeny were fertilized by spermatozoa already residing in the oviduct than would be expected. When the number of spermatozoa inseminated weekly was increased at intervals during a laying cycle, spermatozoa from the initial inseminations were utilized more efficiently, but fertility was depressed at times during the laying cycle. Gradually increasing weekly inseminated numbers of spermatozoa from 50 to 200 million viable cells/hen as the hens age results in nearly equivalent fertility to that resulting from insemination by 200 million cells each week. This represents a savings of 1.4 billion spermatozoa/hen over a 20-wk laying period.}, number={5}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and BAGLEY, LG}, year={1989}, month={May}, pages={724–729} }
 @article{christensen_edens_1985, title={MAGNESIUM, CALCIUM, AND PHOSPHORUS-CONTENT OF SHELLS FROM HATCHING AND NONHATCHING TURKEY EGGS}, volume={64}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0641020}, abstractNote={Shells of hatching and nonhatching Large White turkey eggs were examined for magnesium, calcium, and phosphorus content. Eggshells containing embryos that hatched contained significantly (P less than .05) more magnesium than shells from nonhatching eggs. No differences were seen in their calcium content. Eggshells from pipped eggs contained significantly (P less than .05) more phosphorus than shells from eggs that were not pipped or those that hatched. Calcium and magnesium in turkey eggshells declined as time in lay increased. Injections of exogenous magnesium both at setting and transfer significantly (P less than .05) depressed hatchability, whereas exogenous calcium injected at transfer significantly (P less than .05) improved hatchability. Injections of exogenous calcium at the time of setting significantly (P less than .05) depressed hatchability. It was concluded that the mineral content of turkey eggshells may influence embryo physiology and hatchability.}, number={5}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and EDENS, FW}, year={1985}, pages={1020–1027} }
 @article{christensen_bagley_1984, title={VITAL GAS-EXCHANGE AND HATCHABILITY OF TURKEY EGGS AT HIGH-ALTITUDE}, volume={63}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0631350}, abstractNote={Conductance of turkey eggshells was observed to be significantly (P less than .01) greater at 2000 than at 200 m elevation. It was concluded that the increased conductance may have been due to the Chapman-Enskog relation. Eggshells of nonhatching eggs from the high altitude were examined, and it was determined that despite the increased conductance rate, eggshells with significantly (P less than .05) less functional pore area hatched poorly in both oxygenated and nonoxygenated environments. When oxygen was not supplemented to the incubators at high altitudes, eggshells required significantly (P less than .01) fewer pore concentrations to allow embryos to survive to late stages of embryonic development than eggs in oxygen supplemented environments. However, greater pore concentrations on the air space were required in both environments to complete hatching. Cuticle removal from eggshells incubated in oxygen supplemented incubators at high altitudes significantly (P less than .05) reduced late embryonic mortality. It was concluded that eggshell cuticle removal may be more advantageous to hatchability at high altitude than oxygen supplementation.}, number={7}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and BAGLEY, RA}, year={1984}, pages={1350–1356} }
 @article{christensen_1983, title={DISTRIBUTION OF PORES ON HATCHING AND NONHATCHING TURKEY EGGS}, volume={62}, ISSN={["1525-3171"]}, DOI={10.3382/ps.0621312}, abstractNote={Eggshells from hatching turkey eggs were observed to have significantly (P<.01) more pores on the air space and at the equator than eggshells from nonhatching eggs. Pore concentrations at the small end of eggs were significantly (P<.01) less in eggshells from embryos that died during pipping than in eggshells containing embryos which hatched. A significant (P<.0001) interaction between time of the laying cycle and hatchability of eggs was noted among pore distributions. Pipped but nonhatching eggs laid early in a cycle had greater pore concentrations on their air space and equator than corresponding eggs which hatched. The converse was true for mid and late cycle eggs. It is proposed that the distribution of pores on a turkey egg contributes to embryonic livability.}, number={7}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL}, year={1983}, pages={1312–1316} }
 @article{christensen_mccorkle_1982, title={CHARACTERIZATION OF INCUBATIONAL EGG WEIGHT LOSSES IN 3 TYPES OF TURKEYS}, volume={61}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0610848}, abstractNote={Abstract Incubational egg weight losses of eggs from three types of turkeys were compared three times during a 20-week laying period to determine how increased egg weight affects the water vapor loss of turkey eggs during incubation. One type of hens selected was Large White recycled hens (LW2) in which preincubation egg weight was constant throughout the laying period, whereas the remaining two types, Large White first cycle (LW1) and Small White first cycle (SW1) hens, were selected such that preincubation egg weight increased during the laying period. The LW1 turkey eggs lost the greatest percentage of their preincubation egg weight, SW1 turkey eggs were intermediate, and LW2 turkey eggs lost the smallest percentage. Turkey eggs laid early in a laying period lost less weight than eggs laid in the middle portion, and eggs laid in the mid portion lost less weight than eggs from the late portion. The amount of water vapor lost per unit of shell area as well as the shell conductance data were similar for all hen types and times of the laying period. Increases in preincubational egg weight, egg surface area, and their resulting increased incubational egg weight losses occurred principally during the first 10 weeks of the egg production period in both LW1 and SW1 hens’ eggs.}, number={5}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and MCCORKLE, FM}, year={1982}, pages={848–854} }
 @article{christensen_mccorkle_1982, title={TURKEY EGG WEIGHT LOSSES AND EMBRYONIC MORTALITY DURING INCUBATION}, volume={61}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0611209}, abstractNote={Abstract Shell conductances (mg H2 O·day–1 ·torr–1) of fertile and infertile turkey eggs did not differ significantly after days 7, 14, 21, or 25 of incubation. Furthermore, conductances of eggs that subsequently hatched, contained early dead embryos, or contained late dead embryos did not differ significantly before 7 days of incubation. For the incubation periods 7 to 14, 14 to 21, and 21 to 25 days, eggs with embryos dying late in the course of incubation had significantly lower conductances than eggs with embryos that subsequently hatched or eggs that had died early during development. Fertile and infertile eggs did not differ significantly in egg weight, surface area, percentage of initial egg mass lost during incubation, or amount of water vapor lost per square centimeter of surface area. Similarly, no significant differences were observed between eggs with embryos that hatched normally and eggs with embryos dying early in incubation for any of the aforementioned parameters, but eggs with embryos dying late in incubation had significantly lower percentage of initial egg mass lost and lower amounts of water vapor lost per square centimeter of surface area. Eggs exhibiting late embryonic mortality had the same egg weights and surface areas as the other hatchability groups. It was concluded that gaseous conductance of some turkey eggshells is insufficient to meet embryonic demands late in incubation.}, number={6}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL and MCCORKLE, FM}, year={1982}, pages={1209–1213} }
 @article{christensen_1981, title={EFFECT OF INSEMINATION INTERVALS ON OVIDUCAL SPERM STORAGE IN TURKEYS}, volume={60}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0602150}, abstractNote={Filling and emptying of sperm storage sites of the turkey oviduct were studied using tandem inseminations with semen from bronze and white males. Fertility was better among hens inseminated at weekly intervals than those inseminated at biweekly intervals. The rate of gland filling and emptying was unaffected by weekly and biweekly insemination intervals. However, gland filling and emptying were affected when the birds were inseminated early in a reproductive cycle, and stratification of spermatozoa occurred within the sperm-host glands. Stratification may have occurred to a lesser degree late in the reproductive cycle. It is suggested that sperm storage glands fill and empty at the same rates early and late in a breeding cycle, but fewer glands contain spermatozoa in the latter part of the season, resulting in a decreased fertility.}, number={9}, journal={POULTRY SCIENCE}, author={CHRISTENSEN, VL}, year={1981}, pages={2150–2156} }