@article{picha_biga_galt_mcginty_gross_hedgpeth_siopes_borski_2014, title={Overcompensation of circulating and local insulin-like growth factor-1 during catch-up growth in hybrid striped bass (Morone chrysops Chi Morone saxatilis) following temperature and feeding manipulations}, volume={428}, ISSN={["1873-5622"]}, DOI={10.1016/j.aquaculture.2014.02.028}, abstractNote={Teleosts and other aquatic ectotherms have the ability to withstand prolonged periods of low water temperatures (cold-acclimation) and fasting, and can often respond with phases of accelerated (compensatory) growth when favorable conditions are restored. We assessed whether complete feed restriction prior to (24 °C, days 0–23) and/or during (14 °C, days 24–114) a simulated period of cold-acclimation could elicit episodes of compensatory growth (CG) and catch-up growth upon warm-up to 24 °C and satiation feeding (days 115–148). Control hybrid striped bass (HSB: Morone chrysops × Morone saxatilis) were fed to satiation throughout the entire experiment under these temperature fluctuations. Compensatory growth and ultimately catch-up growth were achieved in groups of HSB that were deprived of feed during either the initial period at 24 °C (days 0–23), during the cold-acclimation period (14 °C, days 24–114), or during both of these periods (days 0–114). Further, it appears that HSB are better able to compensate for weight loss when skeletal length is not significantly compromised during the treatment period, which occurred in HSB feed restricted during cold-acclimation only. The most dramatic CG responses were defined by specific growth rates (SGRs) up to 4.2 times that of controls and were accompanied by hyperphagia and improvements in temporal and overall feed conversion. Levels of plasma insulin-like growth factor (IGF)-1 and muscle IGF-1 mRNA were significantly correlated to growth rate for all groups throughout the experiment (R2 = 0.40, 0.23, respectively), with an overcompensation of both observed in HSB with the most elevated SGRs during the CG response. Interestingly, opposing trends were observed between muscle mRNA expression of growth hormone receptor (GHR)-1 and -2, with fasting at 24 °C and 14 °C resulting in depressed levels of GHR-1 and elevated levels of GHR-2 relative to controls. Levels of muscle myostatin (MSTN)-1 mRNA were significantly depressed in HSB fasted at 24 °C and/or 14 °C while MSTN-2 mRNA was lower following initial feed restriction at 24 °C. Likewise, levels of unprocessed pro-MSTN (precursor) and mature MSTN protein were both depressed in fasted fish at 24 °C. This study demonstrates that a previous period of feed restriction and cold-acclimation followed by realimentation at more favorable water temperatures produces a strong CG response and catch-up growth in fish. These studies also suggest that an overcompensation of circulating and local IGF-1 along with changes in MSTN mRNA and protein expression may contribute to accelerated growth rates characteristic of CG. Furthermore, our studies indicate that overall feed conversion can improve by as much as 30% with CG induced through temperature and feeding manipulations with no adverse effects on growth of HSB. This raises the possibility that CG protocols can improve production efficiency of HSB and other temperate teleosts in pond or tank culture.}, journal={AQUACULTURE}, author={Picha, Matthew E. and Biga, Peggy R. and Galt, Nicholas and McGinty, Andy S. and Gross, Kevin and Hedgpeth, Vickie S. and Siopes, Thomas D. and Borski, Russell J.}, year={2014}, month={May}, pages={174–183} }
 @article{steinman_valenzuela_siopes_millam_2013, title={Tuberal hypothalamic expression of the glial intermediate filaments, glial fibrillary acidic protein and vimentin across the turkey hen (Meleagris gallopavo) reproductive cycle: Further evidence for a role of glial structural plasticity in seasonal reproduction}, volume={193}, ISSN={["1095-6840"]}, DOI={10.1016/j.ygcen.2013.08.001}, abstractNote={Glia regulate the hypothalamic-pituitary-gonadal (HPG) axis in birds and mammals. This is accomplished mechanically by ensheathing gonadotrophin-releasing hormone I (GnRH) nerve terminals thereby blocking access to the pituitary blood supply, or chemically in a paracrine manner. Such regulation requires appropriate spatial associations between glia and nerve terminals. Female turkeys (Meleagris gallopavo) use day length as a primary breeding cue. Long days activate the HPG-axis until the hen enters a photorefractory state when previously stimulatory day lengths no longer support HPG-axis activity. Hens must then be exposed to short days before reactivation of the reproductive axis occurs. As adult hens have discrete inactive reproductive states in addition to a fertile state, they are useful for examining the glial contribution to reproductive function. We immunostained tuberal hypothalami from short and long-day photosensitive hens, plus long-day photorefractory hens to examine expression of two intermediate filaments that affect glial morphology: glial fibrillary acidic protein (GFAP) and vimentin. GFAP expression was drastically reduced in the central median eminence of long day photosensitive hens, especially within the internal zone. Vimentin expression was similar among groups. However, vimentin-immunoreactive fibers abutting the portal vasculature were significantly negatively correlated with GFAP expression in the median eminence, which is consistent with our hypothesis for a reciprocal relationship between GFAP and vimentin expression. It appears that up-regulation of GFAP expression in the central median eminence of turkey hens is associated with periods of reproductive quiescence and that photofractoriness is associated with the lack of a glial cytoskeletal response to long days.}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Steinman, Michael Q. and Valenzuela, Anthony E. and Siopes, Thomas D. and Millam, James R.}, year={2013}, month={Nov}, pages={141–148} }
 @article{siopes_millam_steinman_2010, title={Initiating egg production in turkey breeder hens: Thyroid hormone involvement}, volume={89}, ISSN={["1525-3171"]}, DOI={10.3382/ps.2010-00642}, abstractNote={The role of thyroid hormones in the expression of photosensitivity-photorefractoriness in female turkeys was investigated through the use of an antithyroidal agent, 6-n-propyl-2-thiouracil (PTU). In experiment 1, females held continuously from hatch on long day lengths (16L:8D; LD) and fed 0.1% PTU from 0 to 16 wk, began laying eggs at 26 wk of age, peaking at 75% hen-day egg production by 29 wk, whereas controls initiated lay 3 wk earlier but only achieved less than 50% hen-day egg production. In experiment 2, PTU treatment from 10 to 18 wk severely suppressed plasma triiodothyronine and thyroxine, as confirmed by RIA. Egg production of PTU and control hens held on LD from hatch began by 23 wk, with PTU hens reaching a substantially greater rate of lay than controls. Eggs were smaller initially in both treatments but exceeded 75 g by 28 wk. In experiment 3, recycled hens on short day lengths (8L:16D) received PTU for 2 wk before LD and 12 wk thereafter; a subset of these hens was killed after 48 h of LD for immunohistochemical analysis of fos-related antigen (FRA) expression in the tuberal hypothalamus as a marker of photoinduced neuronal activity. The PTU treatment completely forestalled egg production until its withdrawal; egg production then rose sharply to control levels before resuming, along with controls, a typical seasonal decline. The PTU treatment did not impair photoinduced FRA expression. Together, these results demonstrate the following: 1) that a period of pharmacological suppression of triiodothyronine and thyroxine can substitute for short day exposure in conferring photosensitivity on juvenile-aged turkeys (and is actually superior to short day exposure), 2) that reproductive development does not limit egg production of turkey hens photostimulated as young as approximately 20 wk of age, and 3) that effects of thyroid suppression on photostimulation lie downstream of photoinduced FRA expression. Taken together, these results suggest that there is ample physiological potential to substantially advance the age of photoinduced egg production in commercial flocks.}, number={10}, journal={POULTRY SCIENCE}, author={Siopes, T. D. and Millam, J. R. and Steinman, M. Q.}, year={2010}, month={Oct}, pages={2265–2272} }
 @article{siopes_2010, title={Initiation of egg production by turkey breeder hens: Sexual maturation and age at lighting}, volume={89}, ISSN={["0032-5791"]}, DOI={10.3382/ps.2009-00463}, abstractNote={Experiments were completed addressing photo-responsiveness in juvenile Large White turkey breeder hens, the age at sexual maturity, and the earliest age at photostimulation for egg production using conventional lighting management. In the first experiment, hens were photostimulated at 8 or 16 wk of age with a daily photoperiod of 16L:8D after receiving 8L:16D from hatch. Controls received 16L:8D continuously from hatch. In experiment 2, hens were given naturally declining long day lengths from hatch to 14 wk of age, a daily photoperiod of 8L:16D for the next 10 wk, and were then photostimulated at 24 wk of age with a daily photoperiod of 16L:8D. Data were collected by pen for the onset and rate of egg production, BW, and egg weight. The hens reached sexual maturity and laid eggs as early as 21 to 22 wk of age and the weight for the first 7 eggs was 56.1 g +/- 1.5. The hens were not photoresponsive to photoinduced egg production at 16 wk of age but were fully responsive by 24 wk of age as compared with controls. Photostimulation at 24 wk of age resulted in a slight delay in onset of lay (4 to 5 d) but otherwise typical egg production. These hens produced 113.3 eggs per hen to 54 wk of age as compared with 95.2 eggs for controls photostimulated at the more conventional 30 wk of age. Egg weight was 73.0 versus 80.0 g for the first 7 eggs laid for hens photostimulated at 24 wk of age versus 30 wk of age. At 36 wk of age, egg weights were similar (84.0 vs. 83.7 g). We may conclude that Large White turkey breeder hens can become sexually mature and lay eggs as early as about 22 wk of age. Appropriate pre-lay short day exposure is required to fully photosensitize juvenile hens for photoinduced egg production and this requires a development time beyond 16 wk of age. Photostimulation of fully photosensitive hens for a typical production period can occur as early as 24 wk of age. We demonstrated that the conventional age at lighting of 29 to 30 wk of age can be significantly advanced.}, number={7}, journal={POULTRY SCIENCE}, author={Siopes, T. D.}, year={2010}, month={Jul}, pages={1490–1496} }
 @article{siopes_proudman_2009, title={Exposure duration to long day lengths associated with the expression of photorefractoriness in turkey breeder hens}, volume={88}, ISSN={["1525-3171"]}, DOI={10.3382/ps.2008-00264}, abstractNote={In addition to inducing egg production, exposure to long days concomitantly activates processes that eventually result in photorefractoriness (PR) and cessation of egg production. Experiments were conducted to evaluate the duration of exposure to long days that result in these processes. In each of 3 experiments, we subjected Large White turkey breeder hens to long days (16 or 18 h per day) for differing lengths of time from initial photostimulation and then returned them to a photoperiod (12L:12D) that provided sufficient, but decreased, photoperiodic drive to support egg production but not induce PR. Photoresponsiveness was then evaluated by egg production after a return to a longer day length (20 h per day) late in the lay period and beyond the mean onset of PR typical for these turkey hens. Hens that have undergone any reduction in photoresponsiveness should not increase egg production in response to the increased photoperiod. From experiments 1 and 2, exposure to long days for as little as 1 d and as much as 9 wk from initial photostimulation did not result in an alteration in subsequent photoresponsiveness. This was based on an increased egg production response to a change in photoperiod from 12L:12D to 20L:4D after 20 wk of photostimulation that was similar to controls held continuously on 12L:12D and opposite to the response of controls held continuously on 18L:6D. It was clear that PR had been fully programmed by 20 wk of exposure to long days. Exposure to long days for 12 wk (experiment 3) resulted in a partial alteration of subsequent photoresponsiveness. It was concluded that programming of PR during late spring-summer season occurs after 9 wk of long day exposure, is not fully expressed by 12 wk of long days, and can be fully expressed by 20 wk of photostimulation.}, number={1}, journal={POULTRY SCIENCE}, author={Siopes, T. D. and Proudman, J. A.}, year={2009}, month={Jan}, pages={191–198} }
 @article{siopes_underwood_2008, title={Diurnal variation in the cellular and humoral immune responses of Japanese quail: Role of melatonin}, volume={158}, ISSN={["0016-6480"]}, DOI={10.1016/j.ygcen.2008.07.008}, abstractNote={Experiments were conducted to determine if diurnal variations occur in the cellular and humoral immune responses of sexually mature, male Japanese quail and if this diurnal variation is mediated by the daily rhythm of melatonin. In Experiment 1, quail were exposed to LD 12:12 light-dark cycles and immune responses were measured in response to a single antigenic challenge given to different groups every 4h over a 24h period. Diurnal changes occurred in both the cellular and humoral immune responses. The cellular response was higher during the light phase than during the dark phase whereas the opposite was true for the humoral immune response. Experiment 2 was designed to determine if melatonin mediated these diurnal immune responses. Quail were maintained in continuous light (LL) to suppress endogenous melatonin production and half of them were given melatonin in the drinking water for 12h each day for 2 weeks. Contrary to control quail, significant daily variations occurred in both the humoral and cellular immune responses of birds given melatonin. As in Experiment 1, the cellular and humoral immune responses were out of phase with one another, with the humoral response being maximal when melatonin was present. We may conclude that there exists a melatonin dependent diurnal variation in both cellular and humoral immune responses of quail. The responses were inverse to one another during the daily light-dark cycle with the cellular response being maximal during the daily light period and the humoral response being maximal during the daily dark period.}, number={3}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Siopes, T. D. and Underwood, H. A.}, year={2008}, month={Sep}, pages={245–249} }
 @article{steinman_dinius_siopes_millam_2008, title={Photostimulated expression of type 2 iodothyronine deiodinase mRNA is greatly attenuated in the rostral tuberal Hypothalamus of the photorefractory turkey hen}, volume={20}, DOI={10.1111/j.1365-2826.2008.01781.x}, abstractNote={For many temperate‐zone avian species, termination of breeding occurs when individuals no longer respond to previously stimulatory day lengths, a condition called photorefractoriness. Long day lengths induce significantly greater expression of c‐fos and fos‐related antigens (FRAs) in the tuberal hypothalamus of the photosensitive hen than that of the photorefractory hen. The tuber is also a site of photoinducible glial expression of type 2 iodothyronine deiodinase (Dio2), which converts thyroxine into its active form, triiodothyronine (T3). T3 induces withdrawal of glial processes from gonadotrophin‐releasing hormone (GnRH) I nerve terminals, which is believed to permit the efficient release of GnRH I into the associated portal vasculature. Using a riboprobe, we tested whether long days induce Dio2 mRNA expression in the turkey tuber and, if so, whether this expression is reduced in photorefractory hens. Long days significantly induced rostral and caudal tuberal hypothalamic Dio2 expression in photosensitive hens. Photorefractory hens had reduced expression of Dio2 with most subjects expressing no detectable mRNA in the rostral tuber and variably attenuated amounts throughout the medial and caudal tuber. We also performed double‐label immunohistochemistry to identify co‐localisation between FRAs and glial fibrillary acidic protein, a glial marker. FRAs were present in the nuclei of a few astrocytes in the median eminence and infundibular nucleus of the tuber. The temporal and spatial coincidence between FRA and Dio2 expression, their mutual association with glia, and the attenuation of their response during photorefractoriness suggests that the two events are linked and that photorefractoriness involves a reduced capacity for photo‐inducible gene expression within glia of the tuberal hypothalamus.}, number={11}, journal={Journal of Neuroendocrinology}, author={Steinman, M. Q. and Dinius, S. C. and Siopes, T. D. and Millam, J. R.}, year={2008}, pages={1260–1269} }
 @article{siopes_2007, title={Lighting for summer egg production by turkeys: day length and light intensity}, volume={86}, ISSN={["0032-5791"]}, DOI={10.3382/ps.2007-00245}, abstractNote={This experiment tested the hypothesis that typical poor egg production during the summer is a consequence of insufficient lighting and reduced photoperiodic drive. Large White turkey breeder hens were photostimulated at 30 wk of age with incandescent light on May 12 for summer (off-season) egg production and continued for 28 wk. The lighting treatments were given in a 2 x 2 factorial arrangement with day length and light intensity as main effects. Day lengths used were 15L:9D and 18L:6D, whereas the intensities were 567 +/- 67 and 22 +/- 2 lx. All the treatments were within a light-controlled building, and there were 8 replicate pens of 4 hens for each treatment. Data were collected, by pen, for onset and the rate of lay; BW and feed consumption at 4-wk intervals; and egg weight (EW) at 4-wk intervals including the weight of the first 14 eggs laid, livability, and plasma thyroid hormones for 8 wk postlighting. The rate of egg production through 28 wk of photostimulation was better in the hens receiving 18 than 15 h of light per day (14 eggs/hen difference) but was similar between the 2 intensity treatments. The lower number of eggs in the 15-h group was associated with a greater number of photorefractory hens than in the 18 h of light per day group (39 vs. 14%, respectively). Egg weights were similar between the 18 and 15 h of light/day treatment groups but was significantly greater in the low intensity treatment as compared with the high intensity treatment. We may conclude that by increasing photoperiodic drive by increased day length, but not light intensity, there results an improved summer egg production by turkeys and reduced incidence of photorefractoriness. Egg weight was best at a reduced light intensity.}, number={11}, journal={POULTRY SCIENCE}, author={Siopes, T. D.}, year={2007}, month={Nov}, pages={2413–2419} }
 @article{proudman_siopes_2006, title={Potential role of thyroid hormones and prolactin in the programming of photorefractoriness in turkey hens}, volume={85}, ISSN={["1525-3171"]}, DOI={10.1093/ps/85.8.1457}, abstractNote={The domestic turkey hen is a seasonal breeder, requiring a period of short days to establish photosensitivity and a long day length to initiate egg production. The reproductive season is then limited by the onset of photorefractoriness (PR), which causes a decline, and then termination, of egg laying. In passerine birds, PR is programmed early in the reproductive season by the presence of thyroid hormones and a long photoperiod. High circulating prolactin (PRL) is thought to hasten the onset of PR. In a prior study, we reported that hens destined to have PR exhibited lower levels of thyroxine (T4) and PRL at certain points (weeks) following photostimulation than did hens destined to remain photosensitive (PS), a result opposite to what might be expected. The present study was conducted to further explore the possible relationship between circulating hormone levels and subsequent PR in the commercial turkey hen at times (days) closer to photostimulation than our previous study. Plasma levels of triiodothyronine (T3), T4, and PRL were compared in 2 subpopulations of hens identified retrospectively after 50 wk of egg production: A group of 17 hens that exhibited PR (mean onset = 27 wk of photostimulation) and a group of "good" layers that remained PS (mean production = 210 eggs/50 wk). Results showed no differences between groups in plasma T3 or T4 levels or in the T3:T4 ratio at -6, 0, 1, 3, and 7 d from photostimulation. Plasma PRL levels were significantly higher at 8 and 9 wk after photostimulation in hens that remained PS vs. those that became PR. We conclude that thyroid hormone levels around the time of photostimulation either are not actively related to programming of subsequent PR in turkeys or programming for PR in the turkey hen occurs later in the reproductive cycle than in passerine birds. We further conclude that hens that exhibit PR tend to have lower circulating PRL levels early in the reproductive season than hens that remain PS and lay at a relatively high rate.}, number={8}, journal={POULTRY SCIENCE}, author={Proudman, J. A. and Siopes, T. D.}, year={2006}, month={Aug}, pages={1457–1461} }
 @article{steele_tosini_siopes_underwood_2006, title={Time keeping by the quail's eye: Cireadian regulation of melatonin production}, volume={145}, ISSN={["1095-6840"]}, DOI={10.1016/j.ygcen.2005.09.004}, abstractNote={Previous studies have shown that eye removal disrupts the circadian body temperature and activity rhythms of Japanese quail supporting the hypothesis that the eyes act as pacemakers within the quail circadian system. Furthermore, the putative ocular pacemakers are coupled to the rest of the circadian system via neural and hormonal outputs. Although the neural pathway has yet to be identified, experiments suggest that the daily rhythm of ocular melatonin synthesis and release is the hormonal output. We sought to strengthen the hypothesis that the eyes are the loci of circadian pacemakers, and that melatonin output is involved, by examining melatonin secretion in cultured quail retinas. Using an in vitro flow-through system we demonstrated that (1) isolated retinal tissue could exhibit a rhythm of melatonin release, (2) the rhythm of melatonin synthesis is directly entrainable by 24-h light–dark cycles, and (3) supplementation of the culture medium with serotonin is necessary for robust, rhythmic production of melatonin in constant darkness. These results show definitively that the eyes are the loci of a biological clock and, in light of previous studies showing the disruptive effects of blinding on the circadian system, strengthen the hypothesis that the ocular clock is a circadian pacemaker that can affect the rest of the circadian system via the cyclic synthesis and release of melatonin. The quail retina is proving to be a valuable in vitro model for investigating properties of circadian pacemakers.}, number={3}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Steele, CT and Tosini, G and Siopes, T and Underwood, H}, year={2006}, month={Feb}, pages={232–236} }
 @article{moore_siopes_2005, title={Enhancement of cellular and humoral immunity following embryonic exposure to melatonin in turkeys (Meleagris gallopavo)}, volume={143}, ISSN={["1095-6840"]}, DOI={10.1016/j.ygcen.2005.03.008}, abstractNote={Two experiments were performed to determine the effect of in ovo melatonin supplementation on the ontogeny of immunity in the Large White turkey poult. Different levels of melatonin were injected into the air cell of the egg 4 days prior to hatch. In Experiment 1, turkey embryos received 3 ml of solution containing 200, 100, 50, 25, 10, or 1 microg/ml of melatonin. The hatchability at each dose was determined and compared to vehicle-injected controls. In Experiment 2, only poults from melatonin treatments in Experiment 1 that resulted in normal hatchability (10 and 1 microg/ml) were used. Lymphoproliferative responses to phytohemagglutinin (PHA-P) and primary antibody responses to Chukar red blood cells (CRBC) were determine at five time intervals: 0, 1, 7, 14, and 21 days post-hatch. At each of these times, including 28 days post-hatch, treatment effects on body weights were determined. At 28 days post-hatch, bursal, thymic, and splenic weights were obtained. In ovo melatonin administration significantly accelerated (P0.05) the development of cell-mediated (PHA-P) and humoral (CRBC) immune responses, and these responses were significantly elevated above vehicle-injected controls through 21 days post-hatch. No effect was observed on bursal, thymic, splenic or body weights. These data suggest that embryonic exposure to melatonin enhances post-hatch immune development and responsiveness.}, number={2}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Moore, CB and Siopes, TD}, year={2005}, month={Sep}, pages={178–183} }
 @article{siopes_2005, title={Spontaneous recovery of photosensitivity by turkey breeder hens given prolonged exposure to long day lengths}, volume={84}, ISSN={["1525-3171"]}, DOI={10.1093/ps/84.9.1470}, abstractNote={Three experiments were done to examine spontaneous photosensitivity (SP) and the associated renewal of egg production in Large White turkey breeder hens. In experiment 1, hens were photostimulated with 16 h of light:8 h of dark in December for 54 wk. In experiment 2, SP was examined in a different season than experiment 1. One group of hens was recycled and then photostimulated with 16 h of light:8 h of dark for 23wk. Another group of hens was not recycled and received 16 h of light:8 h of dark throughout the experiment. Egg production was used to assess SP in both experiments 1 and 2. Experiment 3 was designed to produce SP and renewed egg production during prolonged exposure (64 wk) to constant, long day lengths and to evaluate circulating thyroid hormones immediately prior to the renewal of egg production. Egg production was recorded daily to assess SP, and blood samples were taken weekly for radioimmunoassay for thyroid hormones. In both experiments 1 and 2, there was SP and renewed egg production, and this occurred in the fall season. Egg production increased gradually from less than 5% to a peak of 67% (experiment 1) and 38% (experiment 2) in November. In experiment 3, SP occurred in the fall, and egg production increased gradually and was similar to control hens from 8 wk of lay to the end of the experiment. Both groups also had similar declines in egg production following a decrease in photoperiod at wk 24 of the experiment. In the 8-wk period preceding the onset of laying, there were no significant differences between control and SP hens in plasma thyroid hormone levels. In both groups, there was a significant time effect for plasma triiodothyronine, expressed as a parabolic pattern of change. It was concluded that for turkey hens maintained in prolonged and constant long day lengths that SP and renewal of egg production occurs in the fall season. This response was independent of season of photostimulation, did not alter photoresponsiveness to shorten day lengths, and was preceded by a parabolic increase in plasma triiodothyronine.}, number={9}, journal={POULTRY SCIENCE}, author={Siopes, TD}, year={2005}, month={Sep}, pages={1470–1476} }
 @article{proudman_siopes_2005, title={Thyroid hormone and prolactin profiles in male and female turkeys following photostimulation}, volume={84}, ISSN={["1525-3171"]}, DOI={10.1093/ps/84.6.942}, abstractNote={The turkey hen, a photosensitive bird, will become photorefractory (PR) during the reproductive cycle and will cease laying despite a stimulatory day length. This response is thought to be "programmed" by hormonal events early in the reproductive cycle. The turkey tom, in contrast, produces semen for extended periods and has not been shown to exhibit PR. We compared hormone profiles following photostimulation of hens and toms to assess differences that might program one, but not the other, for PR. We photostimulated with 16 h light per day and measured plasma prolactin (PRL), thyroxine (T4), and triiodothyronine (T3) weekly for 12 wk, and again at 16 and 22 wk. Hens were fed ad libitum, and toms were moderately feed-restricted. Results showed increasing PRL levels following photostimulation in hens, with peak levels occurring at about the time of peak egg production, and declining thereafter. Toms maintained significantly lower concentrations of PRL (P < 0.0001) than hens after 2 wk of photostimulation. A highly significant sex by time interaction in plasma T3 levels was observed due to extreme fluctuations in males. Similar, often reciprocal, fluctuations in mean T4 concentrations also occurred in males. We recycled the toms and repeated blood collections under identical conditions, but with ad libitum feeding to determine if feed restriction may have produced these unusual results. This study revealed an initial significant decline in plasma T3 levels and an increase in T4 levels immediately following photostimulation, and then steady (T4) or slowly rising (T3) levels through 12 wk photostimulation. We conclude that PRL profiles of toms and hens differ markedly during the reproductive cycle, lending support to the suggestion that rising PRL may mediate the onset of PR. Further study is needed to determine if the low plasma T3 levels in males may be related to delayed PR. The extreme fluctuations in plasma T3 and T4 levels of toms receiving relatively mild feed restriction suggest a need for further study of the metabolic effects of feed restriction in turkeys.}, number={6}, journal={POULTRY SCIENCE}, author={Proudman, JA and Siopes, TD}, year={2005}, month={Jun}, pages={942–946} }
 @article{proudman_siopes_2004, title={Effect of a single short-term reduction in photoperiod on photorefractoriness in turkey hens}, volume={83}, ISSN={["1525-3171"]}, DOI={10.1093/ps/83.7.1199}, abstractNote={In a prior study, we reported that a high proportion of hens in a winter-laying flock became relatively photorefractory (rPR) early in the reproductive cyand that successive short-term reductions in photoperiod in such hens each initially depressed egg production but then caused a rebound in rate of lay to briefly exceed that of hens that did not exhibit rPR. The present study was conducted to assess rPR in a summer-laying flock and to determine whether a single short-term reduction in day length early in the reproductive cycle might enhance egg production and delay the onset of absolute photorefractoriness (aPR). Control hens received a photoperiod of 16L:8D throughout the experiment. Experimental hens were photostimulated with 16L:8D, received a reduced (but still stimulatory) photoperiod of 11.5L:12.5D for 2 wk beginning 8 wk after photostimulation, and then were returned to 16L:8D for the remainder of the 23-wk test period. Results showed that a single 2-wk reduction in day length shortly after the hens reached peak egg production did not significantly reduce overall flock egg production, but it also did not improve late-season egg production or retard the onset or incidence of aPR. The incidence of rPR was substantially less in this study than we had observed with a winter-laying flock (32.9 vs. 67.1%), but similar proportions of treated hens exhibited the most severe rPR response (a brief but complete cessation of egg production) in both studies (21.1 vs. 24.0%), and all treated hens that subsequently became aPR had shown this severe rPR response to the test photoperiod. We concluded that a core proportion of hens (approximately one-fifth) exhibited a strong rPR response when presented with a reduced photoperiod early in the reproductive cycle, regardless of season of the year, and that such hens were more likely to subsequently exhibit poor egg production or become aPR than flockmates that did not exhibit rPR. Therefore, some indication of the incidence of rPR early in the lay period may have a predictive value for the overall egg production of the flock.}, number={7}, journal={POULTRY SCIENCE}, author={Proudman, JA and Siopes, TD}, year={2004}, month={Jul}, pages={1199–1202} }
 @article{moore_siopes_2004, title={Spontaneous ovarian adenocarcinoma in the domestic turkey breeder hen (Meleagris gallopavo): Effects of photoperiod and melatonin}, volume={25}, number={02-Jan}, journal={Neuroendocrinology Letters}, author={Moore, C. B. and Siopes, T. D.}, year={2004}, pages={94–101} }
 @article{moore_siopes_2003, title={Immune function in turkey breeder hens during the short day prelighting period and renewal of photosensitivity for egg production}, volume={82}, ISSN={["1525-3171"]}, DOI={10.1093/ps/82.1.150}, abstractNote={Photorefractoriness (PR) in the turkey breeder hen is characterized by a lack of responsiveness to photoperiods that previously induced or maintained egg production. The consequence of PR is spontaneous regression of ovarian function and cessation of lay. Photosensitivity (PS) may be regained by giving at least 8 wk of short photoperiod (8L:16D) (light restriction). Following the transition from PR to PS, the birds may be photostimulated with long photoperiods, which allows for the recrudescence of ovarian function and normal egg production. Although the return of reproductive viability is the parameter for determining the successful recycle of ovarian function, there are no known reports of the physiological costs of this transition on immune function in the turkey breeder hen. We conducted an experiment to determine the immune responsiveness at various stages of recycle in the turkey breeder hen. Fifty photorefractory birds were selected and distributed equally among five treatment groups (time points). All birds were given an 8-wk period of light restriction (8L:16D) followed by a 12-wk period of photostimulation (16L:8D). The cellular (cutaneous basophil hypersensitivity CBH) and humoral (antibody titer) immune responses were determined in each treatment group (sequential time points): prelight restriction, 2-wk light restriction, 7-wk light restriction, 2-wk photostimulation, and 12-wk photostimulation. After 2-wk light restriction, there was a reduction in the cellular (64.1%) and humoral (59.5%) immune responses from that of the PR hens at the start. After 7-wk light restriction, the humoral responses increased (33.5%) as compared to the 2-wk light restriction time point Upon photostimulation, both the cellular (23.3%) and humoral (52.4%) immune responses were reduced at 2 wk of photostimulation as compared to the prior 7-wk light restriction time point. Finally, there was a rise in cellular (45.7%) and humoral (72.3%) immune responses after 12 wk of photostimulation as compared to the prior 2-wk photostimulation time point. We concluded that recycling of PR turkey hens was associated with altered cellular and humoral immune responses characterized by initial decline then recovery in both the light restriction and the postphotostimulation periods.}, number={1}, journal={POULTRY SCIENCE}, author={Moore, CB and Siopes, TD}, year={2003}, month={Jan}, pages={150–154} }
 @article{moore_siopes_2003, title={Melatonin enhances cellular and humoral immune responses in the Japanese quail (Coturnix coturnix japonica) via an opiatergic mechanism}, volume={131}, ISSN={["1095-6840"]}, DOI={10.1016/S0016-6480(03)00011-X}, abstractNote={It is known that melatonin has important immunomodulatory properties in the Japanese quail. However, the mechanism of melatonin action on the immune system is not clearly understood in avian species. In mammals, the immunostimulatory properties of melatonin are mediated by the release of opioid peptides from activated T-lymphocytes. The present study was performed to determine if these same melatonin-induced opioids (MIO) are involved with the immunoenhancing effects of melatonin in quail. Three treatment groups were given melatonin (50 microg/ml) in the drinking water ad libitum along with naltrexone, a known opioid receptor-blocking agent. Melatonin was administered throughout the 3 week study and each bird received a daily intramuscular injection of naltrexone at a dose of 0.1, 1.0, or 10.0 mg/kg. In addition, three control groups were established that received only melatonin, naltrexone, or diluent. Evaluation of the cellular and humoral immune responses was initiated after 2 weeks of treatments. A cutaneous basophil hypersensitivity reaction to phytohemagglutinin (PHA-P) was measured to evaluate the cellular immune response. To evaluate the humoral immune response, primary antibody titers were determined 7 days post-intravenous injection with a Chukar red blood cell (CRBC) suspension. Both the cellular and humoral immune responses were significantly increased by 22 and 34%, respectively, upon melatonin exposure as compared to quail receiving diluent only. Concomitant administration of naltrexone and melatonin significantly reduced the immunoenhancing effect of melatonin across all naltrexone doses. We conclude that melatonin enhances a cellular and humoral immune response in Japanese quail via an opiatergic mechanism.}, number={3}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Moore, CB and Siopes, TD}, year={2003}, month={May}, pages={258–263} }
 @article{steele_zivkovic_siopes_underwood_2003, title={Ocular clocks are tightly coupled and act as pacemakers in the circadian system of Japanese quail}, volume={284}, ISSN={["0363-6119"]}, DOI={10.1152/ajpregu.00447.2002}, abstractNote={Our previous studies showed that the eyes of Japanese quail contain a biological clock that drives a daily rhythm of melatonin synthesis. Furthermore, we hypothesized that these ocular clocks are pacemakers because eye removal abolishes freerunning rhythms in constant darkness (DD). If the eyes are indeed acting as pacemakers, we predicted that the two ocular pacemakers in an individual bird must remain in phase in DD and, furthermore, the two ocular pacemakers would rapidly regain coupling after being forced out of phase. These predictions were confirmed by demonstrating that 1) the ocular melatonin rhythms of the two eyes maintained phase for at least 57 days in DD and 2) after ocular pacemakers were forced out of phase by alternately patching the eyes in constant light, two components of body temperature were observed that fused into a consolidated rhythm after 5–6 days in DD, showing pacemaker recoupling. The ability to maintain phase in DD and rapidly recouple after out-of-phase entrainment demonstrates that the eyes are strongly coupled pacemakers that work in synchrony to drive circadian rhythmicity in Japanese quail.}, number={1}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY}, author={Steele, CT and Zivkovic, BD and Siopes, T and Underwood, H}, year={2003}, month={Jan}, pages={R208–R218} }
 @article{siopes_proudman_2003, title={Photoresponsiveness of turkey breeder hens changes during the egg-laying season: Relative and absolute photorefractoriness}, volume={82}, ISSN={["0032-5791"]}, DOI={10.1093/ps/82.6.1042}, abstractNote={Photosensitive species undergo neuroendocrine changes during a reproductive season that cause them to gradually become unresponsive to a photoperiod that initially stimulated reproduction. They may first become relatively photorefractory (rPR), when they will cease egg laying only if photoperiod is reduced, and then absolutely photorefractory (aPR), when they will cease laying despite long day length. Our objective was to test the photoresponsiveness of breeder turkey hens during egg production at various times following photostimulation and to relate photoresponsiveness to rPR and aPR as well as plasma levels of prolactin (PRL) and luteinizing hormone (LH). Hens were maintained in cages in light-controlled facilities and photostimulated at 31 wk of age (September) with a photoperiod of 16L:8D. At 8, 14, and 20 wk after photostimulation, treated hens received a 2-wk exposure to an 11.5L:12.5D photoperiod and were then returned to 16L:8D. Exposure to the shortened photoperiod at 8 wk of photostimulation resulted in three distinct responses of declining egg production: nonresponders (NR, 32.7% of hens), partial responders (PAR, 43.9%), or full responders (FR, 23.4%). Egg production returned to control levels following return to a 16L:8D photoperiod. This response repeated at the 14- and 20-wk treatment periods but with greater declines in egg production in the NR and PAR groups. The incidence of subsequent aPR in the NR, PAR, and FR groups was 5.7, 8.5 and 24%, respectively, as compared to 23.3% for the controls. Plasma LH and PRL concentrations also declined in response to 11.5L:12.5D and also rebounded following return to 16L:8D. The hormonal responses of NR, PAR, and FR were similar. We conclude that turkey hens exhibit varying degrees of rPR early during the egg laying season and that the incidence and severity of the rPR response increases as the laying season progresses. Further, PRL and LH levels did not reflect the differences in egg production among the responder and nonresponder groups to changes in photoperiod.}, number={6}, journal={POULTRY SCIENCE}, author={Siopes, TD and Proudman, JA}, year={2003}, month={Jun}, pages={1042–1048} }
 @article{millam_craig-veit_siopes_2003, title={Photostimulated fos-like immunoreactivity in tuberal hypothalamus of photosensitive vs. photorefractory turkey hens}, volume={134}, ISSN={["0016-6480"]}, DOI={10.1016/S0016-6480(03)00249-1}, abstractNote={Photorefractoriness in commercial turkey hens can be viewed as a failure of previously sexually stimulatory photoperiods to maintain egg production via activation of cGnRH I neurons, but the neural locus of photorefractoriness, i.e., where in the brain failure occurs, is not known. We used a c-fos antiserum that detects c-Fos and Fos-related antigens to characterize Fos-like immunoreactivity (FLI) as a measure of neuronal activation. FLI was measured in somatically mature, photosensitive hens (held on short photoperiods [8L:16D] for at least 10 weeks) before (non-photostimulated-photosensitive group) and after 48 h of exposure to long photoperiods (16L:8D; photostimulated-photosensitive group). We also measured FLI in hens that had become photorefractory, transferred to short photoperiods for 1 week--an insufficient time period to reverse photorefractoriness--and then exposed to long photoperiods for 48 h (photostimulated-photorefractory group). FLI was nearly absent in the tuberal hypothalamus of non-photostimulated-photosensitive hens but FLI was abundant in photostimulated-photosensitive hens. FLI was greatly reduced (P<0.01) in the rostral tuberal hypothalamus of photostimulated-photorefractory hens. All hens showed variable extra-tuberal FLI in locations associated with stress, e.g., paraventricular nucleus, lateral septal area, and nucleus taenia. Double-label fluorescence immunohistochemistry with c-fos antiserum and anti-Neu-N, a neuron-specific protein, showed that a substantial fraction of tuberal FLI-positive cells in photostimulated-photosensitive hens were neuronal. These results implicate neurons in the rostral tuberal hypothalamus as a potential neural locus of photorefractoriness, as FLI in this region appears coupled with cGnRH I activation in photostimulated-photosensitive but not photostimulated-photorefractory turkey hens.}, number={2}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Millam, JR and Craig-Veit, CB and Siopes, TD}, year={2003}, month={Nov}, pages={175–181} }
 @article{millam_wang_craig-veit_siopes_2002, title={Apposition of enkephalinergic axons with cGnRH I-containing perikarya in turkey hen brain}, volume={127}, ISSN={["0016-6480"]}, DOI={10.1016/S0016-6480(02)00029-1}, abstractNote={Several lines of evidence support a role of endogenous opioids in the brain's regulation of gonadotropin secretion in birds and mammals, although the neuroanatomic basis of such regulation is not clear. We used double-label fluorescence immunohistochemistry employing polyclonal antisera raised in sheep against chicken gonadotropin-release hormone I (cGnRH I) and in rabbits against met-enkephalin to determine whether the potential exists for synaptic contact between neurons containing these neuropeptides in the preoptic/septal region of domestic turkey breeder hens. The cGnRH I antiserum was highly specific for cGnRH I, while the met-enkephalin antiserum showed some cross-reactivity with leu-enkephalin. We found numerous instances in which enkephalinergic neuronal elements appeared to contact cGnRH I perikarya and axons in and around the diagonal band of Broca, the bed nucleus of the pallial commissure and in the lateral septal nucleus. These appositions, confirmed by confocal scanning microscopy, appear to provide a neuroanatomic basis for how enkephalinergic innervation might influence gonadotropin secretion in turkey hens by directly regulating activity of cGnRH I neurons.}, number={2}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Millam, JR and Wang, R and Craig-Veit, CB and Siopes, TD}, year={2002}, month={Jun}, pages={128–135} }
 @article{siopes_2002, title={Circulating thyroid hormone levels in recycled turkey breeder hens during a short day prelighting period and renewal of photosensitivity for egg production}, volume={81}, ISSN={["1525-3171"]}, DOI={10.1093/ps/81.9.1342}, abstractNote={Two experiments were conducted with yearling turkey hens at the end of their first season of egg laying. The purpose was to examine changes in plasma thyroid hormone levels during recycling and renewal of photosensitivity for egg production. Plasma concentrations of thyroid hormones were determined weekly or biweekly for 8 wk following a change from existing photoperiods of long days (LD) to short days (SD) and during the associated complete renewal (recycling) of photosensitivity for egg production. In both experiments, neither thyroxine (T4) nor triiodothyronine (T3) declined from starting values during the SD exposure but plasma T3 increased significantly from LD controls. There were no significant treatment effects (SD vs. LD) for T4 in either experiment. The increase in T3 was 101 and 145% in Experiments 1 and 2, respectively, and extended over the 8-wk SD treatment period in a parabolic fashion. The T3/T4 ratio was also significantly increased in the SD treatments of both experiments as compared to LD controls. Plasma concentrations of T3, but not T4, clearly changed during recycling and renewal of photosensitivity for egg production in breeder hens. These results were consistent with a participation of plasma T3 in promoting photosensitivity and diminishing photorefractoriness in turkey hens during SD-induced recycling.}, number={9}, journal={POULTRY SCIENCE}, author={Siopes, TD}, year={2002}, month={Sep}, pages={1342–1346} }
 @article{moore_siopes_2002, title={Effect of melatonin supplementation on the ontogeny of immunity in the Large White turkey poult}, volume={81}, ISSN={["0032-5791"]}, DOI={10.1093/ps/81.12.1898}, abstractNote={An experiment was performed to determine the effect of melatonin supplementation on the ontogeny of immunity in the Large White turkey poult. Melatonin (50 microg/mL) or diluent only (control) was administered via the drinking water from hatch to 28 d of age. The cutaneous basophil hypersensitivity (CBH) reaction to phytohemagglutinin (PHA-P) and primary antibody responses to Chukar red blood cells (CRBC) were determined at five intervals; 0, 1, 7, 14, and 21 d posthatch. At each of these times, including 28 d posthatch, 10 poults were killed and lymphoid organ and body weights were determined. Melatonin administration accelerated (P < or = 0.05) the development of cell-mediated (PHA-P-induced CBH reaction) and humoral (CRBC-induced antibody titer) immune responses, and these responses were elevated above controls through 21 d posthatch. The bursal weight, but not thymus or spleen, was elevated in melatonin treated poults as compared to controls. Body weights were increased in melatonin treated poults as compared to controls. These data suggest that posthatch melatonin supplementation is beneficial to neonatal immune parameters and growth responses of Large White turkey poults.}, number={12}, journal={POULTRY SCIENCE}, author={Moore, CB and Siopes, TD}, year={2002}, month={Dec}, pages={1898–1903} }
 @article{moore_siopes_2002, title={Melatonin can produce immunoenhancement in Japanese quail (Coturnix coturnix japonica) without prior immunosuppression}, volume={129}, ISSN={["1095-6840"]}, DOI={10.1016/S0016-6480(02)00516-6}, abstractNote={In recent years, it has been determined that melatonin has important immunostimulatory properties in mammalian and avian species. Typically, this immunoenhancement has only been examined in immunosuppressed animals. The effect of melatonin on normal (unsuppressed) immune systems is yet to be evaluated in avian species. An experiment was performed to determine if transient and/or continuous melatonin treatments could enhance immune functions in Japanese quail without prior immunosuppression. All quail were kept on a short photoperiod (8:16LD) throughout the study. In this experiment, 50.0μg/ml melatonin was provided ad libitum to adult Japanese quail in the drinking water either continuously or for 3 h per day. Control birds received diluent continuously throughout the experiment. Both the cellular and humoral immune responses were determined immediately after 3 weeks treatment. A cutaneous basophil hypersensitivity reaction to phytohemagglutinin (PHA-P) was measured to evaluate the cellular immune response. To evaluate the humoral immune response, primary antibody titers were calculated 7 days post-intravenous injection with a Chukar red blood cell (CRBC) suspension. The cellular and humoral immune responses were significantly elevated in the transient (3 h) and continuous (24 h) melatonin treatment groups as compared to the control group (0 h). As compared to the control group, the cellular immune response was increased 25% and 38% for the 3 and 24 h melatonin treatments, respectively. The humoral immune response was increased 26% and 32% for the 3 and 24 h melatonin treatments, respectively. Furthermore, continuous (24 h) melatonin availability significantly increased the cellular, but not humoral immune responses as compared to the transient (3 h) group, given melatonin for 3 h prior to the scotophase (13:00–16:00 h). From these data, it was clear that transient and continuous administration of melatonin increased the cellular and humoral immune responses of Japanese quail without prior immunosuppression. These data suggest that the immunoenhancing effect of melatonin is not limited to reconstitution of weakened immune systems, but can be observed in normal, immunologically unsuppressed birds.}, number={2}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Moore, CB and Siopes, TD}, year={2002}, month={Nov}, pages={122–126} }
 @article{siopes_2002, title={Photorefractoriness in turkey breeder hens is affected by age and season}, volume={81}, ISSN={["1525-3171"]}, DOI={10.1093/ps/81.5.689}, abstractNote={Experiments were conducted to determine if the incidence or temporal characteristics of photorefractoriness (PR) in turkey hens were influenced by age or season. Age effects on PR were determined by comparing characteristics of PR in the same hens through two consecutive lay periods. Seasonal influences on PR were evaluated by comparing characteristics of PR in hens photostimulated into lay at different seasons of the year. The onset of PR was evaluated by the spontaneous cessation of lay. Data were collected from daily egg production records for time to onset of PR, time to spontaneous termination of PR, and time required for the transition from photosensitive to the PR state. Percentage incidence, repeatability between consecutive cycles, and persistence (duration) of PR were calculated. Age did not influence the mean time to onset of PR following photostimulation but did affect percentage incidence. All second-year hens (recycled) expressed PR, whereas 89% of the first-year hens did so. Time to onset of PR was not correlated between first- and second-year (recycled) hens. Most, but not all, first-year (84.4%) and recycled (92%) hens were transiently PR and spontaneously terminated PR after 20 to 21 wk of unchanged photoperiod. Hens photostimulated in the winter (December) had delayed mean time to onset of PR from that observed with hens photostimulated in spring (May) by about 7.7 wk. Percentage incidence of PR and duration of PR were similar in both seasons of the year. It was concluded that age and season could affect PR.}, number={5}, journal={POULTRY SCIENCE}, author={Siopes, TD}, year={2002}, month={May}, pages={689–694} }
 @article{moore_siopes_steele_underwood_2002, title={Pineal melatonin secretion, but not ocular melatonin secretion, is sufficient to maintain normal immune responses in Japanese quail (Coturnix coturnix japonica)}, volume={126}, ISSN={["0016-6480"]}, DOI={10.1016/S0016-6480(02)00011-4}, abstractNote={Reports that plasma melatonin is an important immune regulator in avian species have been rather sparse and contradictory. Also, the primary source of immune-modulating melatonin has yet to be determined in birds. In Japanese quail (Coturnix coturnix japonica), the pineal gland and eyes contribute roughly two thirds and one third of the melatonin found in the blood, respectively. Two experiments were conducted to evaluate melatonin as an immune modulator in Japanese quail and to determine the primary source of immune-modulating melatonin in this species. Experiment 1 was designed to evaluate the involvement of the pineal gland and the eyes in immunocompetence. Each of three groups of quail was assigned a surgical treatment and the cellular and humoral immune responses were determined 8 weeks following surgery. The surgical treatments were pinealectomy (Px), sham pinealectomy (SH-Px), and ocular enucleation (eye removal (Ex)). Experiment 2 utilized exogenous melatonin as a replacement to reconstitute immune responses in surgically immunocompromised birds. In this experiment, 50.0 microg/ml of melatonin, or diluent only, was provided to Px and SH-Px birds in the drinking water ad libitum. The cellular and humoral immune responses were determined after 8 weeks of melatonin treatment. In both experiments, a cutaneous basophil hypersensitivity reaction to phytohemagglutinin was measured to evaluate the cellular immune response. To evaluate the humoral immune response, primary antibody titers were determined 7 days postintravenous injection with a Chukar red blood cell suspension. Flow cytometric analysis of peripheral blood lymphocytes was performed to determine the relative percentage of CD4(+) and CD8(+) T- and B-lymphocytes in all treatments of Experiment 2. In Experiment 1, both the SH-Px and Ex surgical treatments produced similar cellular and humoral immune responses, and these responses were significantly greater than those in Px-treated birds. Pinealectomy significantly reduced the cellular and humoral immune responses from SH-Px by 25.8% and 41.3%, respectively. In Experiment 2, Px again resulted in depressed cellular and humoral immune responses. In addition, Px significantly reduced CD8(+) T-lymphocyte numbers compared to SH-Px, while B-lymphocytes remained unchanged. Melatonin administration to Px birds increased the cellular (32.9%) and humoral (30.6%) immune responses to the level of control (SH-Px) birds, although this reconstitution was not due to increased CD8(+) T- or B-lymphocytes. From these data, it was clear that removal of the pineal gland, but not the eyes, reduced cellular and humoral immune responses, which were reconstituted to normal levels by exogenous melatonin. These data suggest that immunodepression is only observed in birds with two thirds of the plasma melatonin removed by pinealectomy. Removal of one third of the plasma melatonin (by ocular enucleation) is not sufficient to reduce cellular and humoral responses in the Japanese quail.}, number={3}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Moore, CB and Siopes, TD and Steele, CT and Underwood, H}, year={2002}, month={May}, pages={352–358} }
 @article{proudman_siopes_2002, title={Relative and absolute photorefractoriness in turkey hens: Profiles of prolactin, thyroxine, and triiodothyronine early in the reproductive cycle}, volume={81}, ISSN={["0032-5791"]}, DOI={10.1093/ps/81.8.1218}, abstractNote={An experiment was conducted to determine whether a commercial strain of turkey hens exhibits relative photorefractoriness (rPR) during a reproductive cycle and to ascertain whether plasma levels of certain hormones early in the reproductive cycle might be associated with subsequent expression of rPR or absolute photorefractoriness (aPR). Twenty-seven percent of hens maintained on a stimulatory photoperiod of 18L:6D for 19 wk and then given a shorter, but still stimulatory, photoperiod (13L:11D) ceased to lay and their ovaries regressed within 4 wk. These hens were considered rPR. Subsequent exposure to the 18L:6D photoperiod resulted in ovarian recrudescence in 41.7% of these PR individuals, confirming the presence of rPR at 19 wk after photostimulation. Absolute PR was observed in 15.1% of hens during a 27-wk reproductive season. Hens that became rPR or aPR exhibited significantly lower plasma prolactin levels at 8 and 14 wk after photostimulation than did hens that remained photosensitive (PS). Plasma levels of thyroxine were lower at 1 and 2 wk following photostimulation in hens that subsequently became PR than in hens that remained PS. We conclude that turkey hens may exhibit rPR and aPR during a reproductive cycle, whereas flockmates may remain PS for at least 27 wk. The presence of long daylengths, thyroid hormones, and PRL did not assure expression of PR. The expression of PR appears to be associated with reduced plasma throxine levels during a period when programming of PR is thought to occur and with reduced levels of prolactin following peak egg production.}, number={8}, journal={POULTRY SCIENCE}, author={Proudman, JA and Siopes, TD}, year={2002}, month={Aug}, pages={1218–1223} }
 @article{siopes_2001, title={Temporal characteristics and incidence of photorefractoriness in turkey hens}, volume={80}, ISSN={["0032-5791"]}, DOI={10.1093/ps/80.1.95}, abstractNote={We conducted experiments to determine the incidence and temporal components of photorefractoriness (PR) in first-year turkey breeder hens after photostimulation. In turkey hens, PR may be defined as a lack of responsiveness to photoperiods that previously induced or maintained egg production and is characterized by a spontaneous cessation of lay, usually followed by molt, as well as an absence of nesting behavior. In one experiment, groups of hens were photostimulated with 18 h of light (L):6 h darkness (D) for 12, 16, 19, or 22 wk and then were exposed to 13L:11D photoperiods to induce a change in egg laying that allowed an evaluation of the photoresponsive state of each group of hens. In two other experiments individual hens were photostimulated continuously with 16L:8D for 24 or 45 wk, and the onset of PR was evaluated by the spontaneous cessation of lay. Data were collected for time to onset of PR, percentage incidence, duration of PR, and the time required for the transition from the photosensitive to the PR state. The earliest onset of PR occurred 7 wk after photostimulation, and the mean onset occurred at about 18 wk of photostimulation. Hens that expressed PR did so within an 18-wk period ending at 25 wk of photostimulation, but not all of these first-year hens expressed PR. Incidence of PR was variable at 59 and 89% in Experiments 2 and 3, respectively. The transition from a photosensitive state to an overt PR state, and therefore a laying to nonlaying state, occurred abruptly within a 2-wk period. Photorefractoriness was permanent during 45 wk of photostimulation for 11% of the PR hens. In the remaining 89% of hens, PR persisted for at least 14 wk (mean of 20.0+/-0.9) but it was not permanent, because they subsequently spontaneously recrudesced. That is, they spontaneously terminated PR. It was concluded that most, but not all, first-year turkey hens become PR and that the incidence is highly variable; PR may be relative or absolute, and absolute PR occurs abruptly but with a highly variable onset time. In most hens, PR is not permanent.}, number={1}, journal={POULTRY SCIENCE}, author={Siopes, TD}, year={2001}, month={Jan}, pages={95–100} }
 @article{zivkovic_underwood_siopes_2000, title={Circadian ovulatory rhythms in Japanese quail: Role of ocular and extraocular pacemakers}, volume={15}, ISSN={["0748-7304"]}, DOI={10.1177/074873040001500211}, abstractNote={ Previous studies have shown that the circadian system of Japanese quail is composed of multiple photic inputs and multiple oscillators. Among these are extraretinal photoreceptors that mediate both circadian and photoperiodic responses and circadian pacemakers in the eyes that, via neural and hormonal outputs, help to maintain rhythmicity of central circadian clocks (presumably located in the suprachiasmatic area of the hypothalamus). Furthermore, a component of the central circadian system is influenced by reproductive hormones. Under certain conditions, the circadian system of female quail can be induced to split into two circadian components: one driven by ocular pacemakers and one driven by feedback from reproductive hormones. Importantly, ovulation is either inhibited or permitted as these two oscillators (or sets of oscillators) constantly change internal phase relationships with each other, suggesting an “internal coincidence” mechanism in the control of ovulation. The oviposition patterns of quail in light-dark (LD) cycles also support an internal coincidence mechanism. The authors tested the hypothesis that the ocular pacemakers are an important component of an internal coincidence mechanism controlling ovulation by examining the effects of blinding by complete eye removal (EX), and the effects of eye-patching, on the body temperature and oviposition patterns of quail exposed to 24-h LD cycles. They also examined the effects of EX on quail exposed to continuous light (LL) and to continuous darkness (DD). Neither EX nor eyepatching affected the oviposition patterns of birds in LD. Furthermore, robust body temperature and oviposition rhythms continued in EX birds in LL, but body temperature became arrhythmic in DD with the cessation of ovulation. The results do not show a role for ocular pacemakers in the control of ovulation, but they do support the hypotheses that (1) entrainment of the central oscillators by extraretinally perceived light is sufficient to preserve a normal ovulatory pattern in LD in the absence of the ocular pacemakers, and (2) in LL, feedback of reproductive hormones onto the central oscillators is sufficient to organize the circadian system even in the absence of the ocular pacemakers. Whether or not the ocular pacemakers are normally involved in the control of ovulation is still an open question. }, number={2}, journal={JOURNAL OF BIOLOGICAL RHYTHMS}, author={Zivkovic, BD and Underwood, H and Siopes, T}, year={2000}, month={Apr}, pages={172–183} }
 @article{moore_siopes_2000, title={Effects of lighting conditions and melatonin supplementation on the cellular and humoral immune responses in Japanese quail Coturnix coturnix japonica}, volume={119}, ISSN={["0016-6480"]}, DOI={10.1006/gcen.2000.7496}, abstractNote={Two experiments were conducted to determine the effects of lighting conditions and melatonin supplementation on the cellular and humoral immune responses in Japanese quail. The first experiment was designed to evaluate differing light regimes as immune modulators in both adult and juvenile quail. The cellular and humoral immune responses were determined for three lighting conditions; short days (8:16LD), long days (16:8LD), and constant light (LL). In the second experiment, melatonin was administered in varying doses to adult quail placed in LL. The doses used in this experiment were 0.0, 0.5, 5.0, and 50.0 microg/ml melatonin given in the drinking water for 16 h per day for 2 weeks. The cellular and humoral immune responses were evaluated after 1 week of melatonin treatment. In both experiments, a cutaneous basophil hypersensitivity reaction to phytohemagglutinin (PHA-P) was measured to evaluate the cellular immune response. To evaluate the humoral immune response, primary antibody titers were calculated 7 days postintravenous injection with a Chukar red blood cell suspension. In the adult birds of experiment 1, both the 8:16LD and 16:8LD treatments produced similar cellular and humoral immune responses but these responses were significantly greater than those observed in LL. The juvenile birds held under 8:16LD also had significantly greater cellular and humoral immune responses as compared to juvenile birds held in LL. In experiment 2, there was a clear melatonin dose response on immune function in LL. The humoral immune response increased to a peak at the 5.0 microg/ml dose while the cellular immune response increased across all dose levels. From the present study it was clear that quail placed in daily light-dark cycles (LD), possessing a diurnal rhythm of melatonin, had significantly elevated immune responses as compared to those birds in LL. Furthermore, melatonin supplemented to birds exposed to LL was immuno-enhancing. This suggests that melatonin may be a mediator of the differences seen between LD and LL lighting conditions and may have important immune modulating properties.}, number={1}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Moore, CB and Siopes, TD}, year={2000}, month={Jul}, pages={95–104} }
 @misc{grimes_siopes_1999, title={A survey and overview of lighting practices in the US turkey breeder industry}, volume={8}, ISSN={["1056-6171"]}, DOI={10.1093/japr/8.4.493}, abstractNote={Abstract A survey to address lighting management practices was sent to members of the turkey breeder industry. Surveys representing 39 complexes were returned. The results indicate that members of the turkey breeder industry have a good basic understanding of light management. However, there was variation in response to some of the questions. Most of the respondents photostimulate their hens with 14 to 15 hr of light/day; the next-highest number gradually increase the day length to 16 to 18 hr/day. High pressure sodium (HPS) lights were indicated as the most common light source, followed by incandescent and fluorescent. Half of the respondents use phase shifting of light; the majority indicated that they do not use intermittent or step-down/step-up lighting programs. Most indicated that they are satisfied with their lighting programs but indicated interest or concern for improving their programs, especially with respect to the proper light intensity for specific ages or reproductive stages of their breeder turkeys. A discussion of light and light management is provided.}, number={4}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Grimes, JL and Siopes, TD}, year={1999}, pages={493–498} }
 @article{siopes_neely_1999, title={Ahemeral lighting of turkey breeder hens. 3. Temporary application and early age at lighting}, volume={78}, ISSN={["0032-5791"]}, DOI={10.1093/ps/78.3.387}, abstractNote={Ahemeral (non-24 h) light-dark cycles are known to increase egg size but when applied continuously have adverse effects on egg production. The purpose of this experiment was to determine whether temporary application of ahemeral light-dark cycles (AH) can overcome the adverse effects of continuous AH and provide improved reproductive performance of turkey hens photostimulated at an early age. Of particular interest was the effect of temporary AH on increasing egg weight at the start of lay because decreased egg weight is a major problem associated with early lighting of turkey hens. The AH treatments started at 26 wk of age and were given for 2 wk, 5 wk, or continuously. Each consisted of 15 h of light per cycle with a cycle length of 28 h duration, that is, 15 h light (L):13 h dark (D). The experiment was started in the winter season and continued for 28 wk. The following variables were measured: BW, feed intake, onset and rate of lay, fertility, hatchability, incidence of floor eggs, egg weight, poult production, and poult weight. It was clear that 5 wk or more of AH followed by standard lighting (15L:9D) increased initial egg weights from those of 26-wk controls and were similar to those of 30-wk controls. This effect was temporary, as it was absent by 8 wk of photostimulation. Also, cumulative eggs per hen to 54 wk of age were increased by 5 wk of AH treatment as compared to those of controls photo-stimulated at 30 wk of age. These eggs had normal fertility, hatchability, and poults per hen in two evaluation periods. A high incidence of AH floor eggs was reduced to that of the controls following a shift to standard light-dark cycles. We concluded that temporary use of AH at the start of photostimulation is better than continuous use of AH throughout lay and resulted in improved reproductive performance of hens photostimulated at an early age.}, number={3}, journal={POULTRY SCIENCE}, author={Siopes, TD and Neely, ER}, year={1999}, month={Mar}, pages={387–391} }
 @article{knowlton_siopes_rhoads_kirby_1999, title={Effects of transient treatment with 6-N-propyl-2-thiouracil on testis development and function in breeder turkeys}, volume={78}, ISSN={["1525-3171"]}, DOI={10.1093/ps/78.7.999}, abstractNote={Experiments were conducted to address recent reports of precocial testis development or testicular hypertrophy induced by the anti-thyroid agent 6-N-propyl-2-thiouracil (PTU) in domestic fowl and rodents. In three experiments, PTU was administered to male turkeys during different stages of development. The PTU was given in the feed at a concentration of either 0.1 or 0.5% and effects on thyroid hormones were measured. Periods of PTU treatment were 8 to 16 or 10 to 18 wk of age (Experiment 1); 0 to 8, 0 to 16, and 8 to 16 wk of age (Experiment 2); and 8 to 16 and 20 to 35 wk of age (Experiment 3). Data were collected to determine the effect of PTU treatment on testicular growth (weight), sexual maturation (semen onset and plasma testosterone concentrations), and early adult testicular function in terms of semen quantity (semen volume and sperm concentration) and quality (sperm viability and fertilizing ability). The 0.1% PTU treatment at 8 to 16 wk of age in Experiment 1 resulted in greater testis weights and sperm production than those of untreated controls at 24 wk of age. The difference was absent by 36 wk of age. Likewise, in Experiment 2, onset of semen production was advanced by about 2 wk by the 8 to 16 wk treatment as compared to untreated controls (23.3 vs 25.9 wk), although, at 32 and 36 wk of age neither the quantity nor quality of semen were significantly affected. Also in Experiment 2, 0.1% PTU treatment from 0 to 8 or 0 to 16 wk of age delayed the onset of semen production and depressed semen volumes at 32 and 36 wk of age without affecting semen quality. In Experiment 3, the mean age at the onset of semen was not significantly affected by 0.5% PTU treatment from 8 to 16 or 20 to 35 wk of age. In addition, semen volume and quality at 32 and 36 wk of age was similar to controls. It was concluded that antithyroid treatment with PTU was dependent on dose and time of treatment for effects on both sexual development and early reproductive performance. Precocial development and associated hypertrophy of the testes occurred but was transient. Thereafter, during initial reproductive function, semen quantity and quality were normal.}, number={7}, journal={POULTRY SCIENCE}, author={Knowlton, JA and Siopes, TD and Rhoads, ML and Kirby, JD}, year={1999}, month={Jul}, pages={999–1005} }
 @article{siopes_1999, title={Improved effectiveness of artificial insemination of turkey hens associated with ahemeral light-dark cycles and age at photostimulation}, volume={78}, ISSN={["0032-5791"]}, DOI={10.1093/ps/78.6.902}, abstractNote={In lighting studies with turkey hens, long ahemeral (AH; non-24 h) light-dark cycles have consistently resulted in greater, although not statistically significant, fertility than control 24 h light-dark cycles. The present study was designed to further evaluate AH lighting effects on fertility by an evaluation of the effectiveness of artificial insemination (AI) under less than optimal conditions for normal fertility, that is, single AI and early age at lighting. Turkey hens had greater percentage fertility of eggs when photostimulated at 30 wk (95.0) than 26 wk (76.3) of age following single, but not double, AI. Ahemeral lighting dramatically improved the effectiveness of a single AI of hens photostimulated at 26 wk of age as compared to controls (89.3 vs 76.3% fertility, respectively). However, with multiple AI, benefits of AH lighting on fertility exceeding that of control hens was not significant. It may be concluded that AH lighting can dramatically improve the effectiveness of AI under certain adverse conditions, such as early age at lighting and reduced exposure of the hen to sperm.}, number={6}, journal={POULTRY SCIENCE}, author={Siopes, TD}, year={1999}, month={Jun}, pages={902–905} }
 @article{siopes_1999, title={Intermittent lighting increases egg weight and facilitates early photostimulation of turkey breeder hens}, volume={78}, ISSN={["0032-5791"]}, DOI={10.1093/ps/78.7.1040}, abstractNote={A major limitation to reducing the age at photostimulation of turkey breeder hens has been small egg size, especially at the start of lay. The present study was designed to determine whether intermittent lighting (IL) could be used to photostimulate hens at an early age (26 wk) and enhance the typical small egg size at the start of lay. Control hens were photostimulated with standard [16 h light (L):8 h dark (D)] lighting at 26 or 30 wk of age. An additional group of hens was photostimulated with IL (2L:12D:2L:8D) from 26 to 32 wk of age and then switched to 16L:8D thereafter. Data were collected for BW, onset of lay, egg production, and egg weight to 54 wk of age. Although IL delayed onset of lay there was no adverse effect on rate of lay because numbers of eggs per hen in 24 wk of photostimulation (30 to 54 wk of age) were similar to that of controls. However, because hens in the IL treatment were photostimulated at 26 wk of age they produced about 10 more eggs per hen (P = 0.18) to 54 wk of age than control hens photostimulated at 30 wk of age. In addition, IL increased egg weight during the first 7 d of lay by about 5% as compared to those of controls also photostimulated at 26 wk of age. Interestingly, the increased egg weight in the IL treatment persisted to the end of lay, well after IL had been switched to 16L:8D. Thus, IL lighting facilitated successful early lighting of hens.}, number={7}, journal={POULTRY SCIENCE}, author={Siopes, TD}, year={1999}, month={Jul}, pages={1040–1043} }
 @article{siopes_1998, title={Absence of a seasonal effect on the critical day length for photorefractoriness in turkey breeder hens}, volume={77}, ISSN={["0032-5791"]}, DOI={10.1093/ps/77.1.145}, abstractNote={Two experiments were conducted to determine whether the critical day length (CDL) for photorefractoriness remained stable or varied by season of the year. The first experiment was done in the fall with photosensitive hens that were exposed to fixed day length treatments ranging from 12 to 16 h/d for 24 wk. At 24 wk of treatment, all hens were given 20 h light (L):4 h dark (D) and subsequent changes in egg production were used to evaluate photorefractoriness. This experimental approach was the same as that used by Siopes (1994) to estimate the CDL for photorefractoriness in winter-photostimulated hens. It was determined that the CDL for photorefractoriness in fall-photostimulated hens was 12 to 12.5 h, the same as that obtained in the earlier report for winter-photostimulated hens. A second experiment was done to further test the possibility that the CDL for photorefractoriness was static during the year. A gradually increasing photoperiod was started in winter at 12L:12D, just under the CDL for photorefractoriness but just over the CDL for egg production. Subsequent egg production and expression of photorefractoriness were compared to controls to estimate the dynamics of the CDL for photorefractoriness. Results supported a static CDL for photorefractoriness and suggest that any daily photoperiod exceeding 12 h will activate processes leading to photorefractoriness, independent of season.}, number={1}, journal={POULTRY SCIENCE}, author={Siopes, TD}, year={1998}, month={Jan}, pages={145–149} }
 @article{siopes_neely_1997, title={Ahemeral lighting of turkey breeder hens .1. Cycle length effects on egg production and egg characteristics}, volume={76}, ISSN={["0032-5791"]}, DOI={10.1093/ps/76.5.761}, abstractNote={A study was conducted to determine the effective range of light-dark cycle lengths for reproductive performance in turkey hens. The treatments consisted of seven different light-dark cycle lengths: 21, 23, 24, 26, 27, 28, and 30 h each with a 15-h photophase per cycle. Data were collected for BW, feed intake, livability, onset and rate of egg production, egg weight (EW), shell thickness, and weight of egg components. The results indicate that turkey hens can be induced to lay eggs with light-dark cycle lengths other than 24 h (ahemeral) with practical extremes being about 23 to 28 h. Egg production in the ahemeral treatments never significantly exceeded that occurring in the 24 h group and the percentage of floor eggs increased at cycle lengths greater than 26 h and at 21 h. Cycle lengths of 21 and 30 h provided the most extreme deviations in the quantity and quality of eggs from those obtained on a 24 h cycle length. Shell thickness increased consistently as cycle lengths increased from 23 to 30 h. Egg weight increased in a curvilinear manner as cycle lengths increased or decreased from 24 h. This increase was associated with increases in shell, yolk, and albumen weight; however, the contribution by each was inconsistent, varying by cycle length as well as time on treatment. It may be concluded that an effective practical range of light-dark cycles for turkeys is 23 to 28 h and that 28 h is a reasonable limit to maximize EW and shell thickness while minimizing a reduction in egg production.}, number={5}, journal={POULTRY SCIENCE}, author={Siopes, TD and Neely, ER}, year={1997}, month={May}, pages={761–766} }
 @article{siopes_neely_1997, title={Ahemeral lighting of turkey breeder hens. 2. Early age at lighting and reproductive performance}, volume={76}, ISSN={["0032-5791"]}, DOI={10.1093/ps/76.12.1783}, abstractNote={An experiment was conducted to determine whether ahemeral lighting (AH) could be used to obtain increased egg weight and poult weight and otherwise normal reproductive performance in Large White turkey hens lit as early as 26 wk of age. The experimental design utilized a 2 x 2 factorial arrangement of treatments that evaluated two light cycle lengths (24 h, control and 28 h, ahemeral) at two hen ages (26 and 30 wk). Treatments were continued for 24 wk and the following variables were measured: BW, feed intake, onset and rate of lay, fertility, hatchability, incidence of floor eggs, egg weight, poult production, and poult weight. As compared to the response of hens in the control lighting treatment, ahemeral lighting increased egg weight and poult weight early in the lay period only and resulted in delayed onset of lay (+3.4 d) and depressed egg production (-7 eggs to 54 wk of age). Percentage fertility and hatchability were similar between ahemeral and control treatment groups. However, ahemeral lighting decreased the number of poults per hen when started at 26, but not 30, wk of age. Hens photostimulated early at 26 wk of age were delayed in onset of lay by 5.9 d but produced more eggs per hen to 54 wk of age (95.8) than hens photostimulated at 30 wk (89.7); however, during equivalent lay periods, egg production was similar between the two groups. Early lighting did not have an adverse effect on fertility, hatchability, or poults per hen but egg weight and poult weight were depressed. It was concluded that although ahemeral lighting increased egg weight and poult weight in turkey hens photostimulated early, continuous application of ahemeral lighting throughout the lay period had adverse effects on some components of reproductive performance.}, number={12}, journal={POULTRY SCIENCE}, author={Siopes, TD and Neely, ER}, year={1997}, month={Dec}, pages={1783–1788} }
 @article{underwood_siopes_edmonds_1997, title={Eye and gonad: Role in the dual-oscillator circadian system of female Japanese quail}, volume={272}, ISSN={["0363-6119"]}, DOI={10.1152/ajpregu.1997.272.1.r172}, abstractNote={ Experiments were conducted to determine the anatomic and physiological basis of the dual-oscillator circadian system of female Japanese quail. After blocking of ocular light perception by eye-patching, the circadian body temperature rhythm dissociates into two circadian components in continuous lighting (LL). One component free runs with a period significantly shorter than 24 h [mean period (tau) = 22.7 h] and is driven by an ocular pacemaker, whereas the other component free runs with a period significantly longer than 24 h (tau = 26.3 h). The long free-running rhythm is driven by the same circadian clock that drives the circadian rhythm of ovulation. The expression of the long free-running rhythm in LL depends on the presence of the ovary: body temperature rhythmicity is abolished by ovariectomy. The two free-running oscillators in eye-patched birds showed evidence of mutual interaction. Significantly, the phase relationships that occur as the two oscillators interact can determine whether or not ovulation occurs. The results are discussed in terms of an "internal coincidence" mechanism for photoperiodic time measurement. }, number={1}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY}, author={Underwood, H and Siopes, T and Edmonds, K}, year={1997}, month={Jan}, pages={R172–R182} }
 @article{siopes_1997, title={Transient hypothyroidism reinitiates egg laying in turkey breeder hens: Termination of photorefractoriness by propylthiouracil}, volume={76}, ISSN={["0032-5791"]}, DOI={10.1093/ps/76.12.1776}, abstractNote={A study was conducted to determine the effects of transient hypothyroidism induced by propylthiouracil (PTU) on termination of photorefractoriness and reinitiation of lay in turkey breeder hens. The PTU was given for 6- or 8-wk periods via the feed and at various doses to yearling hens that had been continuously exposed to long photoperiods [16 h light (L):8 h dark (D)] for at least 25 wk. There was a dose-dependent cessation of lay as well as deletion of thyroxine (T4) and triiodothyronine (T3) during the treatment period. Hens receiving 0.1% PTU or more had little or no circulating thyroid hormones after 2 wk of treatment. Furthermore, resumption of a normal rate and duration of egg laying occurred following withdrawal of the PTU, without any changes in photoperiod. However, this effect only occurred in those hens that had received PTU doses of 0.1% or more and only when the treatment had been given for greater than 6 wk. The resumption of normal levels of egg laying occurred in the absence of a typical preceding molt. Body weights, livability, and fertility and hatchability of eggs from these hens were similar to those of controls. Clearly, turkey hens can be effectively recycled by pharmacological manipulation of the thyroid gland and the results are supportive of thyroid hormone(s) involvement in maintaining photorefractoriness in turkey hens.}, number={12}, journal={POULTRY SCIENCE}, author={Siopes, T}, year={1997}, month={Dec}, pages={1776–1782} }
 @article{siopes_1995, title={INCIDENCE OF PRELAY SQUATTING BEHAVIOR IS NOT RELATED TO SUBSEQUENT EGG-LAYING IN TURKEY BREEDER HENS}, volume={74}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0741039}, abstractNote={Sexual receptivity of turkey hens as indicated by squatting (sexual crouch) was evaluated in three strains of breeder hens, Nicholas (N), Hybrid (H), and British United (B). The incidence of squatting was compared among strains through 84 d of photostimulation and related to egg production characteristics. Significant strain, time, and strain by time interaction effects occurred for the incidence of squatting. In all three strains, squatting started within the 1st wk of photostimulation, rapidly peaked (75.0, 65.6, and 43.0% for H, B, and N hens, respectively) at 14 d of photostimulation, then returned to lower, basal levels at or before attainment of 50% hen-day egg production. Squatting incidence was highly variable within and between strains but was generally lower in N hens than H and B hens, which showed similar squatting expression. The incidence of prelay squatting was not correlated to onset or rate of egg production. However, there was a negative correlation between squatting behavior and percentage floor eggs in H (P = .03) hens. It was concluded that squatting incidence varies within and between strains of hens and is not related to subsequent egg laying performance.}, number={6}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1995}, month={Jun}, pages={1039–1043} }
 @article{siopes_1995, title={TURKEY BREEDER HEN PERFORMANCE BY STRAIN DURING CONSECUTIVE LAY PERIODS}, volume={74}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0741269}, abstractNote={The results of this study provide information about reproductive performance among commercially available strains of Large White Turkey breeder hens, Nicholas (N), British United (B), and Hybrid (H). The hens were managed identically through two consecutive lay periods, summer-fall (1st-yr) followed by winter-spring (recycled). Effects of the intensity (351 vs 24 lx) of supplemental light were evaluated during the 1st-yr lay period. Data were collected for onset of oviposition, egg production, BW, feed consumption, livability, egg weight, and egg components. Light intensity had similar effects on all variables measured. There were neither strain differences nor genetic interactions with light intensity treatment. There was no difference in livability among strains (P = .20) or between year of lay (P = .08), and there was no strain by year interaction. Body weight differed by strains and year and there was a significant strain by year interaction. In general, N were heavier than H or B in the 1st-yr and early recycle lay period, whereas H and B were similar in BW in both lay periods. Recycled hens of all strains were heavier than 1st-yr hens. The onset of lay was earlier in H than B or N in both lay periods and all three strains had a delay in onset of lay after recycling. Through 23 wk photostimulation the B hens produced more eggs per hen than N or H hens (B > N > H) and recycled hens produced more eggs per hen than 1st-yr hens. Strain, year, and strain by year interaction effects were significant for egg weight. The first eggs laid, as well as subsequent eggs in both lay periods, were heaviest in N hens. In all strains, percentage yolk increased and albumen decreased with time in lay. However, N hens had a smaller percentage yolk and greater albumen than H or B hens. The mean percentage shell was greatest in H hens.}, number={8}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1995}, month={Aug}, pages={1269–1279} }
 @article{siopes_1994, title={CRITICAL DAY LENGTHS FOR EGG-PRODUCTION AND HOTOREFRACTORINESS IN THE DOMESTIC TURKEY}, volume={73}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0731906}, abstractNote={Critical day lengths (CDL) for ovarian growth, egg production, and photorefractoriness were estimated in turkey hens during winter and summer seasons. In two experiments, one in each season, fixed day length treatments ranging from 10.5 to 16 h/d were applied to photosensitive hens at 30 wk of age. Daily egg production was used to estimate CDL for the induction of egg production as well as optimal egg production. After 24 wk on light treatments, hens used during the winter season were exposed to 20 h light: 4 h dark and subsequent changes in egg production were used to evaluate photorefractoriness. In two additional experiments, a night-interruption design was used to evaluate CDL and ovarian photoresponsiveness during winter and summer. The CDL for inducing egg production varied by season and was estimated to be 10.5 h or less during winter and about 11 h during summer. Likewise, the CDL for optimal egg production varied by season, being 11 to 11.5 h during winter and > 14 h during summer. The CDL for photorefractoriness in winter photostimulated hens was between 12 and 12.5 h. It was concluded that CDL vary by season and are not fixed, but are dynamic characteristics of photoperiodic processes. Thus, photoresponsiveness of turkey hens changes by season. In addition, CDL for initiating egg production, stimulating egg production, and inducing photorefractoriness are all different, with the CDL for photorefractoriness being longest.}, number={12}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1994}, month={Dec}, pages={1906–1913} }
 @article{siopes_baughman_parkhurst_1993, title={PHOTOPERIOD AND SEASONAL INFLUENCES ON THE GROWTH OF TURKEY HENS}, volume={34}, ISSN={["0007-1668"]}, DOI={10.1080/00071669308417561}, abstractNote={1. The influence of photoperiod and time of year on the growth of hen turkeys was investigated. 2. Photoperiod treatments consisted of computer simulations of day lengths which occur naturally in the spring and autumn of the year. Both photoperiod treatments were given to hens in the autumn and spring. 3. Data were collected for growth evaluations at 2- to 4-week intervals to 16 weeks of age. No significant season X photoperiod interactions occurred. 4. The spring trial resulted in greater body weights and better food conversions (food/gain) than the autumn trial. 5. Simulated autumn daylengths resulted in greater body weights and improved food efficiency at 16 weeks of age compared with simulated spring daylengths. 6. The pattern of growth (period changes) was influenced by season, but not photoperiod. 7. Season and photoperiod both have important and independent influences on the growth of the turkey hen.}, number={1}, journal={BRITISH POULTRY SCIENCE}, author={SIOPES, TD and BAUGHMAN, GR and PARKHURST, CR}, year={1993}, month={Mar}, pages={43–51} }
 @article{siopes_1992, title={EFFECT OF LIGHT-INTENSITY LEVEL DURING PRELAY LIGHT RESTRICTION ON SUBSEQUENT REPRODUCTIVE-PERFORMANCE OF TURKEY BREEDER HENS}, volume={71}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0710939}, abstractNote={Two trials were conducted to determine whether light intensity levels during the prelay (light restriction) and the lay (egg production) periods influenced subsequent photoinduced reproductive performance of turkey breeder hens. The light intensity levels were 22 and 270 lx and each was provided during the prelay and lay periods in a factorial arrangement. Each of the period light intensity levels were applied to half of the hens from each prelay treatment group. Data were collected for BW, rate of reproductive development, egg production, fertility, hatchability, egg weight, and poult weight. There were no interactions between the prelay and lay period treatments, nor a consistent prelay light intensity effect on rate of initiation of lay or duration of time to achieve 50% production. In addition, prelay and lay light intensity levels had no consistent effects on rate of lay, percentage of fertility and hatchability, egg weight, and poult weight. It was concluded that there was no advantage to the use of high-intensity light during short-day light restriction of the prelay period on subsequent reproductive performance.}, number={6}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1992}, month={Jun}, pages={939–944} }
 @article{siopes_1992, title={EFFECTS OF AGE AT LIGHTING ON REPRODUCTION OF TURKEY HENS}, volume={71}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0712099}, abstractNote={Two experiments were conducted to evaluate age at photostimulation on subsequent reproductive performance of Large White turkey hens. All hens were exposed to short daylengths [8 h light (L):16 h dark (D)] for a minimum of 8 wk immediately prior to photostimulation with long day-lengths (16L:8D). Photostimulation started at either 24, 26, 28, or 30 wk of age during January and February (Experiment 1) or July and August (Experiment 2). Data were collected for body weight, time to onset of lay, egg production, and livability in both experiments. In addition, egg quality, broodiness, floor egg production, and poult weight data were obtained in Experiment 2. An inverse relationship occurred between initiation of egg production and the age at lighting up to 30 wk of age. However, peak egg production level and the number of eggs produced per hen during the first 20 wk of egg laying were similar among treatment groups in both experiments. The number of soft-shelled or shell-less eggs produced was also similar among treatment groups. Hens photostimulated at 30 wk of age in Experiment 2 laid the heaviest eggs throughout 20 wk of egg production. Poult weight was reduced when hens were photostimulated at 24 or 26 wk of age, but this only occurred in the first 11 wk of lay. Even though Large White hens responded to photostimulation at 24 wk of age, the results do not support advancing the age at photostimulation to 28 wk or earlier.}, number={12}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1992}, month={Dec}, pages={2099–2105} }
 @article{siopes_1991, title={LIGHT-INTENSITY EFFECTS ON REPRODUCTIVE-PERFORMANCE OF TURKEY BREEDER HENS}, volume={70}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0702049}, abstractNote={Two trials were conducted to evaluate the reproductive performance of turkey hens to different light intensity during the lay period. In Trial 1 the hens were exposed to 16 h of light (L) and 8 h dark (D) per day (16L:8D) at 54, 108, or 216 lx and in Trial 2 a 2 x 2 factorial arrangement of treatments was used with main treatment factors being intensity level (54 versus 324 lx) and photoperiod (16L:8D versus 14L:10D). Data were collected for time to onset of lay, rate of lay, fertility, hatchability, and egg and poult weight in both trials, and feed intake in Trial 1. In both trials the light intensity treatments were similarly effective in the photoinduction of reproductive performance in Large White turkey hens. This occurred with daily photoperiods of both 14L:10D and 16L:8D in Trial 2 and there was no photoperiod by intensity interaction. There were no significant differences in feed intake or feed efficiency among the 54-, 108-, and 216-lx treatments of Trial 1. It may be concluded that reproductive performance of turkey hens in closed confinement is equivalent within an intensity range of 54 to 324 lx.}, number={10}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1991}, month={Oct}, pages={2049–2054} }
 @article{siopes_1991, title={LIGHT-INTENSITY FOR TURKEY BREEDER HENS - DEGREE OF DARKNESS REQUIRED DURING SHORT-DAY LIGHT RESTRICTION AND INTENSITY THRESHOLD DURING PHOTOSTIMULATION}, volume={70}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0701333}, abstractNote={Abstract Responses of Large White turkey breeder hens to various light intensities were examined with respect to the degree of darkness required during short-day light restriction and intensity threshold during photoinduction of egg laying. For degree of darkness required during light restriction, hens were given 0 (control), .5, 1.5, 2, or 3 lx light intensity during the daily dark phase (brownout) of short-day [6 h light (L): 18 h dark (D)] light restriction treatment (Experiment 1). Treatments were given from 24 to 32 wk of age and their effects on terminating juvenile photorefractoriness were evaluated during a subsequent photoinduced (16L: 8D) egg production cycle. In addition, these same treatments were applied from 58 to 66 wk of age to the same hens to evaluate their effectiveness in terminating egg production. The brownout treatment neither terminated photorefractoriness in young hens nor completely terminated lay in yearling hens. For light intensity threshold evaluations during photostimulation of egg production, two consecutive experiments were conducted in which 32-wk-old photosensitive hens were photostimulated with 16 h of light/day (16L:8D) at light intensities of .5, 1.1, 2.2, 4.3, and 43 lx. In both experiments, a light treatment as low as .5 lx caused all hens to lay eggs. The time to onset of lay was delayed in the .5-lx treatment group of both experiments and the 1-lx treatment group of Experiment 3 relative to other intensities. Thus, the effective threshold for typical onset of lay in turkeys is about 2.2 lx but the threshold for initiation of lay is .5 lx or less. In both experiments, the 43-lx treatment group produced the most eggs per hen but the difference from other treatment groups was significant only in Experiment 2. Eggs per hen among the remaining treatment groups were similar in both experiments. It may be concluded that 1) the absolute degree of darkness (threshold) required during light restriction to effectively terminate photorefractoriness and induce photosensitivity in turkey hens is less than .5 lx; and 2) initiation of egg laying has a low light intensity threshold of .5 lx or less.}, number={6}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1991}, month={Jun}, pages={1333–1338} }
 @article{siopes_pyrzak_1990, title={EFFECT OF INTERMITTENT LIGHTING ON THE REPRODUCTIVE-PERFORMANCE OF 1ST-YEAR AND RECYCLED TURKEY HENS}, volume={69}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0690142}, abstractNote={In each of two trials, a 2-by-2 factorial arrangement of treatments was utilized to evaluate the reproductive performance of first-year and recycled turkey hens to intermittent lighting (IL) through an egg-laying period of 20 wk. The IL treatment provided 4 h of light per day given as 2 h light:12 h dark:2 h light:8 h dark (2L:12D:2L:8D). This treatment group was compared to controls maintained on 16L:8D. Data were collected for BW, feed intake, feed efficiency, time to first egg, eggs per hen fertility, hatchability, egg weight, and poult weight. Consistent age effects included greater BW, egg weight, and poult weight from recycled hens compared to first-year hens as well as a delay in the onset of laying and a reduction in egg production by six eggs per hen in the recycled hens. Feed intake and feed efficiency were similar in both age groups, Intermittent lighting delayed the onset of laying but increased the rate of lay by eight eggs per hen. Late-season fertility, feed efficiency, and egg weight were significantly increased by the IL treatment. The conclusion was that, for turkey hens, intermittent lighting can effectively improve reproductive performance.}, number={1}, journal={POULTRY SCIENCE}, author={SIOPES, TD and PYRZAK, R}, year={1990}, month={Jan}, pages={142–149} }
 @article{siopes_elhalawani_1989, title={PINEAL AND OCULAR INFLUENCES ON MALE AND FEMALE TURKEYS - PLASMA LUTEINIZING-HORMONE AND PROLACTIN LEVELS DURING GONADAL DEVELOPMENT}, volume={73}, ISSN={["1095-6840"]}, DOI={10.1016/0016-6480(89)90101-9}, abstractNote={Plasma levels of prolactin (PRL) and luteinizing hormone (LH) were determined in pinealectomized (PX) and/or bilateral ocular enucleated (EX) turkey hens and toms during gonadal development. Measurements were obtained weekly for 6 weeks following photo-induced ovarian recrudescence in adult hens and biweekly from 12 to 34 weeks of age in sexually developing toms. Both hens and toms were maintained on a photoperiod of 16L:8D. Plasma PRL levels were significantly correlated with time (P < 0.01) and were linear with significant slopes (P < 0.01) in all treatment groups of hens and toms. However, the regression coefficients were positive for the hens and negative for the toms. Both PX and EX reduced PRL levels in the hens. PX did not significantly affect PRL levels of toms but EX depressed PRL levels. In hens LH was not correlated with weeks of photostimulation but in toms LH was positively correlated to age and linear with significant slopes in all treatment groups. There were no significant treatment effects on plasma LH levels of hens or toms. It was concluded that neither the pineal gland nor the eyes effect plasma LH levels of male turkeys during testicular development or female turkeys during photostimulated ovarian recrudescence. Although the eyes affected plasma PRL of both males and females during gonadal development, the pineal only influenced female PRL levels.}, number={2}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={SIOPES, TD and ELHALAWANI, ME}, year={1989}, month={Feb}, pages={284–292} }
 @article{siopes_1989, title={PRELAY LIGHT RESTRICTION OF TURKEY HENS - DAYLENGTH VERSUS EXPOSURE TIME}, volume={68}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0681337}, abstractNote={A 3 x 3 factorial experimental design was used to examine the relationship between the duration of short daylength (10, 8, or 4 h light/day) during prelay light restriction and the length of time (12, 8, or 6 wk) that young turkey hens were exposed to light restriction and subsequent photoinduced reproductive performance. Data were collected for time to first egg, egg production, percentage of fertility, and hatchability, and poult weight. Light restrictions consisting of 10, 8, or 4 h light/day were equally effective in terminating photorefractoriness and preparing hens for subsequent photoinduced reproductive performance. A 6-wk exposure to light restriction did not prepare hens for egg laying as effectively as 8 (P less than .05) or 12 (P less than .10) wk of exposure, both of which were similarly effective. A lack of interaction between the light restriction daylength and exposure time suggests that the requirements for effective light restriction are rather specific and cannot be beneficially manipulated by various combinations of daylength and weeks of exposure.}, number={10}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1989}, month={Oct}, pages={1337–1341} }
 @article{siopes_baughman_parkhurst_timmons_1989, title={RELATIONSHIP BETWEEN DURATION AND INTENSITY OF ENVIRONMENTAL LIGHT ON THE GROWTH-PERFORMANCE OF MALE TURKEYS}, volume={68}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0681428}, abstractNote={In each of two trials a 2 x 2 factorial arrangement of treatments was used to evaluate the growth response of tom turkeys to environmental light. The main experimental light treatment factors were: daylength [23 h light (L):1 h dark (D) vs. 8 h L:16 h D] and light intensity (10.8 lx vs. 108 lx). There were 100 toms in each treatment; all birds were in closed confinement floor pens exposed to artificial light only. Data were collected for growth performance evaluations at 2 to 4-wk intervals to 22 wk of age. No significant daylength x intensity interactions occurred in the study. No consistent effect of daylength or light intensity on body weight occurred. Light intensity had no significant effect on feed conversion but 23 h L:1 h D significantly (P less than or equal to .01) improved feed conversion from that in the 8 h L:16 h D treatment at 18 and 22 wk of age. This occurred in both trials. Neither the daylength nor the light intensity treatment effects differed with regard to livability or to incidence of leg disorders. Testicular development at 22 wk of age of birds in the two intensity treatments was similar but testes were significantly (P less than .01) larger in the 23 h L:1 h D treatment than the 8 h L:16 h D treatment. Percentage of breast yield was not influenced significantly by the daylength or intensity treatments but the amount of abdominal fat was significantly greater in the 8 h L:16 h D group than the 23 h L:1 h D group. From the results of this study it seems clear that daylength can have an important impact on the growth performance of tom turkeys whereas variations in light intensity ranging from 10.8 to 108 lx generally resulted in negligible differences in response.}, number={11}, journal={POULTRY SCIENCE}, author={SIOPES, TD and BAUGHMAN, GR and PARKHURST, CR and TIMMONS, MB}, year={1989}, month={Nov}, pages={1428–1435} }
 @article{siopes_elhalawani_1986, title={PLASMA PROLACTIN AND LUTEINIZING-HORMONE LEVELS OF PINEALECTOMIZED AND ENUCLEATED TURKEY HENS}, volume={62}, ISSN={["0016-6480"]}, DOI={10.1016/0016-6480(86)90091-2}, abstractNote={Plasma levels of LH and prolactin were determined in pinealectomized (PX) and/or bilateral ocular enucleated (EX) adult turkey hens maintained in either constant (24LL) or diurnal (16L:8D) lighting. Blood samples were obtained at the following times over a 24-hr period: onset, middle, and end of light period, middle and end of dark period. In experiment 1, the effects of PX alone were evaluated in photorefractory hens exposed to two different photoperiods (24LL and 16L:8D). In experiment 2, the effects of PX and EX were determined in egg-laying and photorefractory hens exposed to a 16L:8D daily photoperiod. Neither PX nor EX significantly altered LH or prolactin levels of egg laying or photorefractory hens at any of the sampling times of the day in either experiment. In experiment 1, LH levels were very similar in both 16L:8D and 24LL but prolactin levels were significantly lower in 24LL than 16L:8D. It was concluded that the pineal gland does not play an essential role in maintaining circulating LH and prolactin levels in constant light or a photoperiod of 16L:8D.}, number={1}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={SIOPES, TD and ELHALAWANI, ME}, year={1986}, month={Apr}, pages={36–42} }
 @article{siopes_1984, title={RECYCLING TURKEY HENS WITH LOW LIGHT-INTENSITY}, volume={63}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0631449}, abstractNote={Yearling turkey breeder hens were recycled into a second egg production cycle by exposure to 16 hr of light per day (16L:8D) of .5, 2.2, 4.3, or 7.6 lx intensity. Controls were exposed to 6L:18D of 55 lx intensity. At the end of the 8-week recycling treatments, all hens were photostimulated with 16L:8D of 55 lx intensity and the time to first egg and rate of egg production were recorded. Low light intensity terminated photorefractoriness and resulted in egg production comparable to the controls in the .5 lx treatment only. Light intensities of 2.2, 4.3, and 7.6 lx resulted in significantly reduced egg production. Turkey hens can be successfully recycled with a low light intensity of .5 lx but not 2.2 lx or greater.}, number={7}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1984}, pages={1449–1452} }
 @article{siopes_1984, title={THE EFFECT OF FULL-SPECTRUM FLUORESCENT LIGHTING ON REPRODUCTIVE TRAITS OF CAGED TURKEY HENS}, volume={63}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0631122}, abstractNote={Large White turkey breeder hens were exposed to either incandescent or full-spectrum (FS) fluorescent lighting during two 20-week reproductive cycles in closed confinement. Data were recorded for body weights, feed intake, and reproductive traits. Body weights and feed intake were similar between treatments in both egg laying cycles. In addition, there were no significant differences in egg production, fertility, hatchability, or poult weight between the incandescent and FS fluorescent light treatment in either the first or second year egg laying cycle. It was concluded that exposure of breeder turkey hens to FS fluorescent light in closed confinement results in reproductive performance similar to that obtained with incandescent lighting.}, number={6}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1984}, pages={1122–1128} }
 @article{siopes_1984, title={THE EFFECT OF HIGH AND LOW INTENSITY COOL-WHITE FLUORESCENT LIGHTING ON THE REPRODUCTIVE-PERFORMANCE OF TURKEY BREEDER HENS}, volume={63}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0630920}, abstractNote={Large White turkey breeder hens were exposed to incandescent or cool-white (CW) fluorescent light of either high or low light intensity as the sole light source. Light treatments were quantified in both photometric and radiometric units for the entire visible spectrum as well as the 600 to 700 nm range of the visible spectrum. Photostimulation with these light sources occurred at 32 weeks of age and the subsequent effects on body weight, feed intake, and reproductive performance were observed over a 20-week egg laying period. Body weights and feed intakes were similar among the treatments. There were no significant differences in early season egg production (0 to 10 weeks) or fertility, hatchability, egg weight, and egg specific gravity due to light intensity or light source over the 20-week test period. However, CW fluorescent light delayed the onset of egg production from that of hens exposed to incandescent light (20.7 vs. 19.3 days, respectively) and significantly depressed late season (10 to 20 weeks) egg production from that observed in hens on incandescent light (23.9 vs. 31.9 eggs per hen, respectively). As a result, total egg production was significantly lower in the CW fluorescent (67.9 eggs/hen) than the incandescent treatment (75.2 eggs/hen). No significant differences in total eggs per hen occurred between the low and high light intensity treatments.(ABSTRACT TRUNCATED AT 250 WORDS)}, number={5}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1984}, pages={920–926} }
 @article{siopes_burke_1984, title={THE EFFECT OF OVARIECTOMY ON BROODINESS AND PLASMA PROLACTIN LEVELS IN TURKEY HENS DURING A PHOTOINDUCED REPRODUCTIVE-CYCLE}, volume={22}, ISSN={["1879-3231"]}, DOI={10.1016/0093-691X(84)90465-5}, abstractNote={The effects of ovariectomy on broody behavior and plasma prolactin levels were examined in turkey hens that had previous histories of broodiness. Ovariectomy eliminated all nesting behavior and blocked the photostimulated increase in plasma prolactin observed in sham-operated hens. Sham-operated hens demonstrated egg-laying patterns and nesting behavior typical of broody hens. A large increase in plasma prolactin preceded broody behavior which continued as long as the elevated amounts of plasma prolactin persisted. It was concluded that the ovary is essential in expressing broody nesting behavior, the large increase in plasma prolactin associated with this behavior, and the prolactin increase in hens that did not demonstrate nesting behavior.}, number={4}, journal={THERIOGENOLOGY}, author={SIOPES, TD and BURKE, WH}, year={1984}, pages={445–453} }
 @article{siopes_1983, title={EFFECT OF INTERMITTENT LIGHTING ON ENERGY SAVINGS AND SEMEN CHARACTERISTICS OF BREEDER TOM TURKEYS}, volume={62}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0622265}, abstractNote={Large White breeder toms were exposed to one of the following light treatments at 34 weeks of age: 1) 15L:9D (control); 2) 2L:11D:4L:7D; 3) 4L:9D:4L:7D; 4) 2L:11D:2L:9D. After 4, 8, 12, and 18 weeks of exposure to these intermittent light treatments, body weight, feed consumption, and semen quality and quantity were determined. Although they maintain similar body weights, toms on intermittent light consumed less feed, produced equivalent semen volumes with similar sperm numbers, and maintained percent normal sperm more persistently during the summer heat than control toms. Compared to the 15L:9D controls, electrical savings for light as great as 73% was calculated for intermittent light. It was concluded that toms can be maintained more efficiently on intermittent lighting than a standard lighting program of 15 hr of light per day.}, number={11}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1983}, pages={2265–2270} }
 @article{siopes_1983, title={EFFECT OF PINEALECTOMY ON BROODINESS OF TURKEY HENS}, volume={62}, ISSN={["1525-3171"]}, DOI={10.3382/ps.0622245}, abstractNote={Large White breeder hens with a history of broody behavior were recycled into a second reproductive cycle following pinealectomy. Pinealectomy did not alter the performance of broody hens with respect to time to first egg, duration of egg production, eggs per hen, number and duration of egg sequences, number and duration of pauses, time to onset of broody nesting behavior, or persistency of nesting. It was concluded that the pineal gland does not play an essential role in the onset or maintenance of broodiness in turkey hens.}, number={11}, journal={POULTRY SCIENCE}, author={SIOPES, TD}, year={1983}, pages={2245–2248} }
 @article{siopes_1983, title={PERSISTENCY OF BROODINESS IN RECYCLED TURKEY HENS}, volume={20}, ISSN={["0093-691X"]}, DOI={10.1016/0093-691X(83)90080-8}, abstractNote={Large White turkey breeder hens identified as broody during their initial egg production cycle were recycled into a second and third reproductive cycle in order to determine the persistency of broodiness. Egg production data included time to first egg, duration of lay and the number of eggs per hen. Nesting data included time to first broody nesting activity and duration of broody nesting activity. In general, there were no significant differences among the three cycles for the above observations. Mean values over the three cucles were as follows: 24.6 days to first egg following photostimulation; 49.4 days of egg production; 29.4 eggs per hen; 46.9 days from the first egg to first broody nesting and 59.7 days duration of nesting. Of 10 hens identified as broody in their first egg production cycle and followed through two additional 20-week cycles, seven hens demonstrated broody nesting behavior and nine had low rates of egg production. It was concluded that broody traits of a given hen are carried over into subsequent cycles.}, number={5}, journal={THERIOGENOLOGY}, author={SIOPES, TD}, year={1983}, pages={565–569} }
 @article{siopes_timmons_baughman_parkhurst_1983, title={THE EFFECT OF LIGHT-INTENSITY ON THE GROWTH-PERFORMANCE OF MALE TURKEYS}, volume={62}, ISSN={["0032-5791"]}, DOI={10.3382/ps.0622336}, abstractNote={The growth performance of tom turkeys maintained in closed and open confinement housing was examined. Treatments were initiated on the day of hatching and consisted of constant light intensity of 1, 11, 110, or 220 lx in an enclosed house or sunlight supplemented with 11 or 220 lx at night in an open-sided house; all treatments received a total of 23 hr of light each day (23L:1D). Body weight, feed conversion, mortality, leg abnormalities, and final testes weight were recorded. Growth performance at marker age was not significantly different among treatments except for a heavier 18-week body weight in the open-confinement group given sunlight only (DL) and, in the closed confinement, a better feed conversion in the 11 lx treatment (C11) than the 1 lx treatment (C1) at 22 weeks of age. There was no apparent relationship between light intensity level and leg abnormalities but 22-week testes weight increased as light intensity increased. It was concluded that within closed confinement a constant light intensity of 1 lx resulted in an inferior growth performance, whereas 11 lx was sufficient to allow a growth performance similar to that obtained with 110 or 220 lx. In open confinement, supplemental artificial light at night of 11 or 220 lx did not result in an improved growth performance from birds on natural daylengths.}, number={12}, journal={POULTRY SCIENCE}, author={SIOPES, TD and TIMMONS, MB and BAUGHMAN, GR and PARKHURST, CR}, year={1983}, pages={2336–2342} }