@article{edens_ort_ludescher_2014, title={Improved early performance of turkey poults given an Aloe ferox leaf extract with bentonite}, volume={55}, ISSN={["1466-1799"]}, DOI={10.1080/00071668.2014.945898}, abstractNote={Abstract 1. AT-402 (20 g/kg), a proprietary blend of Aloe ferox leaf extract and calcium bentonite, had no adverse effect on poult body weights at 3 weeks of age. 2. Lower body weights and lower feed consumption were observed in 4-week-old poults given 10 and 20 g/kg of AT-402 compared to poults given 0 or 5 g/kg. 3. Floor-reared poults, given either 5 or 10 g/kg AT-402 to 4 weeks of age, were significantly heavier than controls (0 g/kg AT-402), and feed conversion ratios for AT-402 given poults were improved. 4. Xylose uptake in 5 g/kg AT-402-fed poults was significantly greater than in poults given AT-402 at 0 and 10 g/kg, reflecting increased body weights of 5 g/kg AT-402-fed poults. 5. Delayed access by poults to the AT-402 until 10 d of age also improved 4-week body weights, suggesting that the AT-402 might improve performance as soon as it is given. 6. AT-402 at 5 g/kg was most efficacious as demonstrated by improved body weights and feed conversions.}, number={5}, journal={BRITISH POULTRY SCIENCE}, author={Edens, F. W. and Ort, D. T. and Ludescher, B. L.}, year={2014}, month={Sep}, pages={675–683} }
 @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{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{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{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} }
 @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{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{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{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{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{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_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} }