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The effects of duration and variation in photoperiod on testis weight, testicular sperm production, semen output, and hormone status over the reproductive season in male turkeys were investigated. In Experiment 1, four groups of males raised from 17 to 23 wk of age under a constant short photoperiod were subjected to a constant short (Group 1: 7L:17D; Group 2: 10.5L:13.5D), constant long (Group 3: 14L:10D) or progressively increasing photoperiod (Group 4: 7L:17D to 14L:10D) up to 60 wk of age. In Experiment 2, four groups of males first raised as in Experiment 1 up to 23 wk of age were placed under a constant short (Group 5: 10.5L:13.5D), constant long (Group 6: 14L:10D), or night-interrupted photoperiod (Group 7: 6L:2.5D:1L:14.5D, referred to as subjective 9.5L:14.5D; Group 8: 6L:3.5D:1L:13.5D), referred to as subjective 10.5L:13.5D) up to 60 wk of age. Males in Groups 2-4 had similar reproductive characteristics, whereas sexual maturity was delayed from 29 to 49 wk in males from Group 1. In Experiment 2, males in Groups 5 and 8 had similar reproductive characteristics, whereas sexual maturity was delayed in males in Group 7 in a manner similar to that observed in Group 1. In both experiments, plasma LH and testosterone concentrations were poor indicators of testis development and semen production, irrespective of age and photoperiod. We conclude that a moderately short photoperiod such as 10.5L:13.5D or subjective 10.5L:13.5D may stimulate reproductive characteristics of male turkeys in a manner comparable to constant long or increasing photoperiods. We inferred the existence of a threshold of photosensitivity in male turkeys for photoperiods longer than 9.5L:14.5D, but shorter than or equal to 10.5L:13.5D.

The objectives of this study were to identify and quantitate the germ cell populations of the testes in sexually mature male turkeys (Trial 1), determine the duration of meiosis based on BrdU labeling and stereological analyses (Trial 2), and examine the impact of various photoperiods on germinal and somatic cell populations in immature and adult males (Trial 3). In Trial 1, both testes within a male had similar stereological components (P>0.05) for all parameters analyzed. In Trial 2, the duration of Type-1 spermatocytes and round spermatids in turkeys lasted 4.5+/-0.5 and 2.0+/-0.5 days, respectively. In Trial 3, the short photoperiod (7L:17D) delayed testicular growth (in the stereological parameters analyzed). In contrast, the effect of a moderately short photoperiod (10.5L:13.5D) was comparable to the effect of a long (14L:10D) or increasing photoperiod (7L:17D to 14L:10D) on the stereological parameters examined. With the exception of the short photoperiod, all other photoperiods used in this study induced comparable early testicular maturation, with maximum testis weight at 29-35 weeks of age. As the males got older, there was a progressive, linear decline in testis weight through 60 weeks, at which time there were no significant differences among photoperiods. In conclusion, the duration of meiosis in the turkey was similar to that observed in the fowl and guinea-fowl. The existence of a threshold of photosensitivity to gonad stimulation in male turkeys is suggested to be between 7.0 and 10.5 h of light.

1. The effects of the force-feeding procedure and its different components on various physiological indicators of acute and chronic stress were investigated in male mule ducks before and during a 12-d cramming period. 2. The highest concentration of corticosterone were measured after injection of ACTH agonist, during the pre-experimental period when the ducks were still housed in collective floor pens and at the time of transfer. 3. During the cramming period, corticosterone measured before and after force-feeding did not differ significantly though there was a non-significant trend towards an increase in certain cases. 4. The different components of force-feeding, including manipulation, intubation, force-feeding with a standard or a large amount of food had no significant effect upon corticosterone concentrations. 5. There was no indication from ACTH agonist challenge either of a change in adrenal sensitivity or a change in its responsiveness. 6. The heterocyte-lymphocyte ratio measured before and at the end of the cramming period did not differ significantly. 7. In conclusion, we observed no significant indication that force-feeding is perceived as an acute or chronic stress by male mule ducks, in our experimental conditions. Nevertheless, it remains to be shown that their adrenocorticotropic axis is responsive to acute stressors.

The effects of various frequencies of semen collection on several quantitative and qualitative semen characteristics were investigated in adult turkey breeder males (30 to 40 wk of age). In Experiment 1, a total of 35 males were first trained for semen collection (twice a week for 2 consecutive wk), and then divided into five groups (seven males each), each group being collected either once every 2 wk, once every week, twice every week, three times every week (each for 4 wk) or five to seven times per week (each for 2 wk). Volume, sperm concentration, and sperm number per ejaculate were determined for each ejaculate. No significant differences between groups were observed for sperm concentration (P > 0.05), but males collected once every 2 wk, once per week, or twice per week had larger volumes than males collected at higher frequencies (P < 0.05). Thus there were significant differences for sperm number per ejaculate between groups (P < 0.05). Also, daily semen output (DSO) was markedly increased in males collected at the highest frequencies (e.g., DSO = 0.62 x 10(9) and 1.93 x 10(9) in males collected once and five times per week). Finally, in euthanatized birds (36 wk) no differences between groups were observed for body weight (25.8 +/- 1.7 kg), testicular weight (51.5 +/- 2.2 g), or total number of elongated spermatids per male (14.0 +/- 0.8 x 10(9)). In Experiment 2, 35 males were distributed into groups and collected under the same conditions as in Experiment 1. Besides quantitative analyses of ejaculates (volume, sperm concentration, and sperm per ejaculate), sperm viability between groups was also tested using the Sybr14/PI fluorescence test. Our results demonstrated: 1) a favorable effect of high semen collection frequencies on sperm viability and, 2) a marked decline in sperm viability during the first 2 d following a 2-d resting period in males collected five times a week. We concluded that turkey males express their optimal reproductive capacity more efficiently when semen collection is undertaken at a high rather than a low frequency.

1. Changes in plasma corticosterone concentrations according to puncture sites and various challenges including injections of an ACTH agonist (Immediate Synacthen) were investigated in male mule ducks. 2. Lower concentrations were measured in samples drawn by puncture from the occipital sinus than at a wing vein site. 3. Immobilisation and a single intramuscular injection of saline solution (1 ml, 0.9%) had no effect on plasma corticosterone after 15 min. 4. A single intramuscular injection of ACTH (5 microg/kg body weight) produced a rise (P<0.05) in corticosterone. Maximum concentrations were measured after 10 min and, in the absence of further sampling, a return to initial levels was observed by 1 h. 5. On the other hand, repeated bleedings following ACTH challenge maintained higher corticosterone concentrations. 6. A single intramuscular injection of ACTH at doses ranging between 0.625 to 20 microg/kg body weight increased corticosterone concentrations (P<0.05) in a dose-dependent manner, with the responses plateauing at doses of 1.25 microg/kg and higher.