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The Effect of Photoperiod and Feed Restriction on Semen Production in the Turkey
The Effect of Photoperiod and Feed Restriction on Semen Production in the Turkey ALLEN E. WOODARD, R. L. SNYDER, and L. FUQUA Department of Avian Sciences, University of California, Davis, California 95616 (Received for publication May 15, 1978)
INTRODUCTION Unlike t h e female, which is d a r k - d e p e n d e n t , t h e t u r k e y male will reach sexual m a t u r i t y u n d e r a wide range of lighting regimens (Polley et al, 1 9 6 2 ; Ogasawara et al, 1962). Sexually m a t u r e males can be induced t o m o l t u n d e r a 6-week period of n o n s t i m u l a t o r y ( 8 L : 1 6 D ) light and later r e t u r n e d t o semen p r o d u c t i o n u n d e r a period of stimulatory ( 1 6 L : 8 D ) light (Woodard et al, 1 9 7 5 ) . When given 8 hr of nonstimulatory light daily, males u n d e r g o a c o m plete m o l t w i t h i n t h r e e weeks, a n d t e r m i n a t e semen p r o d u c t i o n w i t h i n four weeks. In practice, m o s t commercial flocks of turkeys are k e p t in outside pens where c o n t r o l of t h e d u r a t i o n of natural daylight is impossible. Birds t o b e m o l t e d m u s t be placed in special r o o m s where t h e a m o u n t of light can be regulated. T h e rising cost of c o n s t r u c t i o n is making this m e t h o d of molting less attractive t o t h e t u r k e y grower. Swanson and Bell ( 1 9 7 4 ) have described several systems for molting chickens. These require feed and water deprivation followed b y a period of daily feed restriction. Generally these systems are used w i t h o u t a red u c t i o n in p h o t o p e r i o d . It is n o t k n o w n , h o w ever, if t u r k e y males will t e r m i n a t e semen p r o 1979 Poultry Sci 58:217-221
d u c t i o n u n d e r such conditions w i t h o u t a conc u r r e n t r e d u c t i o n in p h o t o p e r i o d . T h e purposes of this s t u d y were 1) t o determine if a short-term feed and water deprivation, followed b y a 4- or 8-week period of 50% of full feed, with or w i t h o u t a r e d u c t i o n of p h o t o period, would t e r m i n a t e semen p r o d u c t i o n in t u r k e y s , and 2) t o d e t e r m i n e t h e rate of testes regression and recovery in males w h e n cycled t h r o u g h periods of n o n s t i m u l a t o r y ( 8 L : 1 6 D ) a n d s t i m u l a t o r y ( 1 6 L : 8 D ) light. EXPERIMENTAL PROCEDURE In E x p e r i m e n t 1 ( 1 9 7 6 ) , 72 yearling Broad Breasted White t u r k e y males, 5 4 weeks of age, t h a t had c o m p l e t e d a 30-week season of semen p r o d u c t i o n u n d e r 16 hr light per d a y , were divided into six groups of 12 birds each. T h e y were k e p t in individual cages in t e m p e r a t u r e (range from 25 t o 30 C) and light-controlled r o o m s . T h e light t r e a t m e n t s were: G r o u p s 1, 2 , a n d 3 received 8 L : 1 6 D p e r d a y for 8 weeks, and thereafter were given 1 6 L : 8 D . Birds in groups 4 , 5, a n d 6 r e m a i n e d o n 1 6 L : 8 D t h r o u g h o u t t h e test. T h e intensity of light given t o t h e birds during t h e short- and long-day p h o t o p e r i o d s was 5 and 30 lux, respectively.
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ABSTRACT In Experiment 1, 72 yearling Broad Breasted White Turkey males were induced to molt under either stimulatory (16L:8D) or nonstimulatory (8L:16D) light used concurrently with a short period of feed and water deprivation, and followed by periods of daily feed restriction (50% of full feed). One-fourth of the males were killed at intervals of 4, 8, 12, and 16 weeks and their testes weighed. In Experiment 2, 40 yearling Broad Breasted White males were killed at 2-week intervals during an 8-week period of 8 hr light per day followed by a 10-week period of 16 hr light per day. Testes were removed, weighed, and fixed in Bouin's solution for histological preparation. In Experiment 1, birds kept under 16 hr light and given different periods of feed and water deprivation, followed by 8 weeks of feed restriction, failed to terminate semen production, although their testes were reduced substantially in size and function. Other groups of males given 8 hr light per day with concurrent regimens of feed deprivation and daily feed restriction, terminated semen production within 4 weeks. When returned to 16 hr light, the testes were twice as heavy as those of males kept in production during the entire test. In Experiment 2, the testes of birds induced to molt under 8 hr light per day regressed by 73% and 89%, respectively, after 4 and 8 weeks of exposure. When given 16 hr light per day, some spermatogenic activity was noted at 4 weeks, and complete spermatogenesis, with maximum semen production, occurred after 6 weeks. There was evidence that a successful rejuvenation of the testes requires a period of complete quiescence.
WOODARD ET AL.
218
RESULTS
In Experiment 1, only 16% of the birds in groups 4 and 5 had terminated semen production after 8 weeks on 50% of full feed without a concurrent reduction in photoperiod (Figure 1). After completion of their periods of feed restriction, the average semen volumes of birds in groups 4 and 5 that remained in production had decreased approximately 50% and 78%, respectively. None of the birds in the groups kept under 16 hr light molted during the 8-week
period of feed restriction. After given full access to feed, males in group 4 had the most rapid recovery to full semen production, and had exceeded the level of production attained by groups 5 and 6 by approximately 32%. With one exception, all birds given 8 hr light had terminated semen production after 4 weeks, irrespective of the feed regimen. The exception terminated production one week later. Although semen volumes of birds in groups 1 and 2 decreased at a slightly faster rate than those of birds in group 3, all birds terminated semen production at the same time. After given 16 hr light, most birds in groups 1, 2, and 3 began to produce semen within 5 weeks, and were producing near maximum volumes by the 6th week. Birds given a reduction in daily photoperiod began to molt after 3 weeks. Average biweekly body weights of birds kept under the different feed regimens and photoperiods are shown in Figure 2. Birds in groups 1 and 2 lost approximately 17% and 22%, respectively, of their initial body weights during the first 4 weeks of feed restriction. This compares to only a 6% loss in weight for birds in group 3 that were kept on full feed under 8 hr light. After 6 weeks on full feed, the birds in groups 1 and 2 recovered the weight lost, even though they remained under 8 hr light during most of the recovery period. Birds in groups 4 and 5 that were kept under 16 hr light lost approximately 26% of their initial weight during the 8week period of feed restriction. After 8 weeks on full feed, the birds in groups 4 and 5 still weighed approximately 20% and 10% less, respectively, than their initial weights. Average testicular weights of birds killed at 4, 8, 12, and 16 weeks of test are given in Table 1. Irrespective of the feed restriction regimen used, the testes of males kept under & hr light had regressed significantly (P<.05) in weight by 86% after 4 weeks, and by 90% after 8 weeks. When the birds were returned to 16 hr light, the left testis grew slightly faster than the right one, and their combined average weights exceeded that of the controls (group 6) by 10% and 51%, respectively, after the 4th and 8th weeks. However, these differences were not found to be significant due to the variability among birds within treatments. Although most birds in groups 4 and 5 had not terminated semen production during the 8week period of restricted feeding their testicular weights were regressed 17% and 42%, respectively. After 8 weeks on full feed, the testes of
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Water was withheld for the first three days in all groups but 3 and 6. Birds in groups 1 and 4 were deprived of feed for the first 7 days of the test, then were given 50% of full feed for the next 21 and 49 days, respectively. Birds in groups 2 and 5 were deprived of feed for the first 14 days, then were given 50% of full feed for the next 14 and 42 days, respectively. The amount of feed given each bird during the period of feed restriction was 227 g. This value represented about 50% of their daily requirement as determined from measurements made prior to the start of the test. After completion of their periods of feed restriction, all birds were returned to full feed. Birds in group 3 and 6 had free access to feed throughout the test. One-fourth of the birds from each group was killed at 4, 8, 12, or 16 weeks of test. Individual testes were removed and weighed on a Mettler balance sensitive to the nearest .1 mg. Semen was collected weekly using the method of Burrows and Quinn (1939), and volumes were measured in a graduated syringe to the nearest .01 ml. Body weights were obtained biweekly for all birds prior to slaughter. In Experiment 2 (1975), 40 yearling Broad Breasted White turkey males, 54 weeks of age, were housed under conditions described in Test 1. They were given 8 weeks of 8L:16D per day, followed by 10 weeks of 16L:8D per day. Four birds were killed at the start of the test, and groups of four were killed at biweekly intervals. The left testis from each bird was fixed in Bouin's solution, dehydrated in ethyl alchol, and embedded in paraffin. Later, these testes were sectioned and microscopically examined for stage of spermatogenesis. The data on testes weights were subjected to a one-way analysis of variance and significance among means was determined by Tukey's procedure, described in Steel and Torrie (1960) for determining significance (P<.05) among means.
PHOTOPERIOD AND FEED ON SEMEN PRODUCTION
8 WEEKS
FIG. 1. Average biweekly semen volumes from males kept under different light and feed restriction regimens. Treatments:
Light/day
Feeding
Group 1 Group 2 Group 3 Group 4 Group 5 Group 6
8L:16D(8wk)» 8L:16D(8wk)* 8L:16D(8wk) 16L:8D (cont.)* 16L:8D(cont.)* 16L:8D (cont.)
No feed first No feed first Full feed. No feed first No feed first Full feed.
7 days; 50% full feed 21 days. 14 days; 50% full feed 14 days. 7 days; 50% full feed 49 days. 14 days; 50% full feed 42 days.
•No water for first 3 days.
males in groups 4 and 5 were 31% heavier than those of the controls (group 6), but still 25% lighter than the average weights of males in groups 1, 2, and 3. In Experiment 2, four birds were killed every 2 weeks over an 18-week period; their testicular weights are shown in Figure 3. The testes of males exposed for 4 and 8 weeks of 8 hr light per day had regressed 73% and 89%, respectively, from their initial weights. When the birds were returned to 16 hr light, their testes reached near maximum growth by the 6th week of exposure. This weight was approximately 30% greater than that of the initial weight. Semen volumes declined sharply soon after birds were given 8 hr light. Semen was collected from only two of the 28 birds sampled after 4 weeks of test, and that only in trace amounts. When given 16 hr light, birds reached sexual maturity after 5 weeks, and were producing near maximum volumes by the 6th week. Microscopic examination revealed marked differences in size and development to the seminiferous tubules of testes removed after 2
weeks of exposure to nonstimulatory light. Most tubules contained spermatozoa in their lumens. After 4 weeks of exposure to 8 hr light, most tubules were markedly reduced in size, with a spermatogenetically inactive germinal epithelium. After 8 weeks, the seminiferous tubules were very small, with conspicious amounts of interstitial tissue around them. After the birds were returned to 16 hr light, most of the seminiferous tubules still showed some regression after the 4th week of exposure; but by the 6th week, lumens of most tubules contained many spermatozoa.
DISCUSSION The feed restriction regimens used in our study were not of sufficient magnitude or duration to cause termination of semen production in 54-week old sexually active birds kept under 16 hr light. The size and function of the testes closely approached termination of semen production. This was especially indicated for those males in group 5 that had the greatest loss in
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6
219
WOODARD ET AL.
220
18.0 -
..-H
"3 I 7.0 "V*--...
••
*—• 6 ~~'•
*
*-•
~ i6.o£\v O 15.0
8 WEEKS
16
FIG. 2. Average biweekly body weights of males kept under different light and feed restriction regimens Treatments:
Light/day
Feeding regimen
Group Group Group Group Group Group
8L:16D(8 wk)* 8L:16D(8wk)* 8L:16D(8 wk) 16L:8D (cont.)* 16L:8D (cont.)* 16L:8D (cont.)
No feed first No feed first Full feed. No feed first No feed first Full feed.
1 2 3 4 5 6
7 days; 50% full feed 21 days. 14 days; 50% full feed 14 days. 7 days; 50% full feed 49 days. 14 days; 50% full feed 42 days.
*No water for first 3 days. testicular size a n d function. It is q u e s t i o n a b l e , however, t h a n an extension of t h e period of feed restriction given t o males in g r o u p 5 w o u l d have eventually resulted in their t e r m i n a t i o n of semen p r o d u c t i o n . Krueger and co-workers ( 1 9 7 7 ) f o u n d t h a t males, given a daily feed re-
striction of 50% of full feed starting w h e n t h e birds were 18 weeks of age, p r o d u c e d favorable volumes of semen from 32 t o 6 2 weeks of age, even t h o u g h t h e birds were a b o u t 30% ligher in weight t h a n c o m p a r a b l e birds allowed full feed. T h e relationship b e t w e e n size of t h e testes
TABLE 1. Average combined testes weight (g) of birds kept under different light and feed restriction regimens Photoperiod (16L:8D)
Photoperiod (8L:16D)' Groups 3
Groups
(wk)
l2
2
3
4
5
6
4 8 12 16
4.4 C 3.9C 26.1 a 43.4 a
3.0C 3.4= 30.6 a 44.5 a
4.2C 4.2C 34.6 a 46.6 a
16.2abc 18.7 a b 30.4 a 37.0 a
22.4 a b 13.2 b c 33.2 a 29.7 a
30.6 a 24.6 a 31.6 a 22.7 a
' ' Values in the same row having different letters are significantly different (P<.05). Birds in groups 1, 2, and 3 were given stimulatory light (16L:8D) after 8 weeks. Each value represents the average testes weights of 3 bird samples. Group:feeding regimen. 1) No feed 7 days, 50% full feed for 21 days; 2) no feed 14 days, 50% full feed for 14 days; 3) full feed, 4) no feed 7 days, 50% full feed for 49 days; 5) no feed 14 days, 50% full feed for 42 days; and 6) full feed.
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PHOTOPERIOD AND FEED ON SEMEN PRODUCTION
221
tion in old males. This finding m a y lend credence t o o u r previous study (Woodard et al., 1 9 7 5 ) in which recycled males p r o d u c e d a b o u t 20% m o r e semen during a second 20-week period of semen p r o d u c t i o n t h a n did comparable birds k e p t u n d e r c o n s t a n t s t i m u l a t o r y light.
I
Photoperiod (8L:I6D)
1
Photoperiod ( I 6 L : 8 0 )
<
WEEKS
and persistency of semen p r o d u c t i o n is n o t clearly u n d e r s t o o d . Unlike t h e partridge (Alectoris graced), whose testes u n d e r g o rapid regression after 4 weeks of exposure t o 8 hr light (Woodard et al, 1 9 7 8 ) , t h e t u r k e y requires a b o u t 6 t o 8 weeks t o reach c o m p l e t e testicular quiescence (Wilson et al., 1 9 7 6 ) . In t h e present s t u d y males p r e c o n d i t i o n e d u n d e r 8 hr light, t h e n given 16 hr light, had testes t h a t reached m a x i m u m size after 6 weeks. T h e y were twice as heavy as t h o s e of males in group 6, which were allowed t o remain in c o n t i n u o u s p r o d u c t i o n u n d e r 16 hr light, and 26% heavier t h a n t h e average weights of testes of males in groups 4 and 5. These results are in agreement with those of Wilson et al. ( 1 9 7 6 ) , w h o f o u n d t h a t testes weights of yearling males, at t h e start of t h e second recrudescent period, were nearly twice as heavy as those from comparable birds k e p t in semen p r o d u c t i o n u n d e r c o n s t a n t light regimen of 8 hr light 16 hr darkness per day. T h e increase in size of t h e testes following m o l t m a y a c c o u n t for t h e increase in semen p r o d u c -
REFERENCES Burrows, W. H., and J. P. Quinn, 1939. Artificial insemination of chickens and turkeys, USDA Circ. 525. Krueger, K. K., J. A. Owen, C. E. Krueger, and T. M. Ferguson, 1977. Effect of feed or light restriction during the growing and breeding cycles on the reproductive performance of Broad Breasted White turkey males. Poultry Sci. 56:1566—1574. Ogasawara, F. X., W. O. Wilson, and V. S. Asmundson, 1962. The effect of restricting light during the adolescent period on reproductive performance in turkeys subsequently exposed to 12-, 14- and 20hour days. Poultry Sci. 41:1858-1863. Polley, C. R., R. N. Shoffner, R. E. Burger, and E. L. Johnson, 1962. Light regulation in turkey management. 3. Male reproductive performance. Poultry Sci. 41:1570-1573. Steel, R. G. D., and J. H. Torrie, 1960. Principles and procedures of statistics. McGraw-Hill Book Company, Inc., New York. Swanson, M. H., and D. D. Bell, 1974. Force molting of chickens. II. Methods. University of California Coop. Ext. Bull. AXT-411. Wilson, W. O., F. X. Ogasawara, T. D. Siopes, and A. E. Woodard, 1976. Light management of turkey toms. Archiv. fur geflugelkunde 4:147—151. Woodard, A. E., F. X. Ogasawara, R. L. Snyder, and V. Stinnett, 1975. Effect of forced molting on quantity and quality of semen in turkey breeder males as influenced by diet. Poultry Sci. 54:2094— 2101. Woodard, A. E., R. L. Snyder, and L. Fuqua, 1978. Testicular regression and recovery in the chukar partridge as affected by photoperiod. Poultry Sci. 57:298-300.
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FIG. 3. Average biweekly testes weights (g) and semen volumes (ml) from males cycled under 8 weeks of nonstimulatory (8L:16D) light and 10 weeks of stimulatory (16L:8D) light.
INTRODUCTION Unlike t h e female, which is d a r k - d e p e n d e n t , t h e t u r k e y male will reach sexual m a t u r i t y u n d e r a wide range of lighting regimens (Polley et al, 1 9 6 2 ; Ogasawara et al, 1962). Sexually m a t u r e males can be induced t o m o l t u n d e r a 6-week period of n o n s t i m u l a t o r y ( 8 L : 1 6 D ) light and later r e t u r n e d t o semen p r o d u c t i o n u n d e r a period of stimulatory ( 1 6 L : 8 D ) light (Woodard et al, 1 9 7 5 ) . When given 8 hr of nonstimulatory light daily, males u n d e r g o a c o m plete m o l t w i t h i n t h r e e weeks, a n d t e r m i n a t e semen p r o d u c t i o n w i t h i n four weeks. In practice, m o s t commercial flocks of turkeys are k e p t in outside pens where c o n t r o l of t h e d u r a t i o n of natural daylight is impossible. Birds t o b e m o l t e d m u s t be placed in special r o o m s where t h e a m o u n t of light can be regulated. T h e rising cost of c o n s t r u c t i o n is making this m e t h o d of molting less attractive t o t h e t u r k e y grower. Swanson and Bell ( 1 9 7 4 ) have described several systems for molting chickens. These require feed and water deprivation followed b y a period of daily feed restriction. Generally these systems are used w i t h o u t a red u c t i o n in p h o t o p e r i o d . It is n o t k n o w n , h o w ever, if t u r k e y males will t e r m i n a t e semen p r o 1979 Poultry Sci 58:217-221
d u c t i o n u n d e r such conditions w i t h o u t a conc u r r e n t r e d u c t i o n in p h o t o p e r i o d . T h e purposes of this s t u d y were 1) t o determine if a short-term feed and water deprivation, followed b y a 4- or 8-week period of 50% of full feed, with or w i t h o u t a r e d u c t i o n of p h o t o period, would t e r m i n a t e semen p r o d u c t i o n in t u r k e y s , and 2) t o d e t e r m i n e t h e rate of testes regression and recovery in males w h e n cycled t h r o u g h periods of n o n s t i m u l a t o r y ( 8 L : 1 6 D ) a n d s t i m u l a t o r y ( 1 6 L : 8 D ) light. EXPERIMENTAL PROCEDURE In E x p e r i m e n t 1 ( 1 9 7 6 ) , 72 yearling Broad Breasted White t u r k e y males, 5 4 weeks of age, t h a t had c o m p l e t e d a 30-week season of semen p r o d u c t i o n u n d e r 16 hr light per d a y , were divided into six groups of 12 birds each. T h e y were k e p t in individual cages in t e m p e r a t u r e (range from 25 t o 30 C) and light-controlled r o o m s . T h e light t r e a t m e n t s were: G r o u p s 1, 2 , a n d 3 received 8 L : 1 6 D p e r d a y for 8 weeks, and thereafter were given 1 6 L : 8 D . Birds in groups 4 , 5, a n d 6 r e m a i n e d o n 1 6 L : 8 D t h r o u g h o u t t h e test. T h e intensity of light given t o t h e birds during t h e short- and long-day p h o t o p e r i o d s was 5 and 30 lux, respectively.
217
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ABSTRACT In Experiment 1, 72 yearling Broad Breasted White Turkey males were induced to molt under either stimulatory (16L:8D) or nonstimulatory (8L:16D) light used concurrently with a short period of feed and water deprivation, and followed by periods of daily feed restriction (50% of full feed). One-fourth of the males were killed at intervals of 4, 8, 12, and 16 weeks and their testes weighed. In Experiment 2, 40 yearling Broad Breasted White males were killed at 2-week intervals during an 8-week period of 8 hr light per day followed by a 10-week period of 16 hr light per day. Testes were removed, weighed, and fixed in Bouin's solution for histological preparation. In Experiment 1, birds kept under 16 hr light and given different periods of feed and water deprivation, followed by 8 weeks of feed restriction, failed to terminate semen production, although their testes were reduced substantially in size and function. Other groups of males given 8 hr light per day with concurrent regimens of feed deprivation and daily feed restriction, terminated semen production within 4 weeks. When returned to 16 hr light, the testes were twice as heavy as those of males kept in production during the entire test. In Experiment 2, the testes of birds induced to molt under 8 hr light per day regressed by 73% and 89%, respectively, after 4 and 8 weeks of exposure. When given 16 hr light per day, some spermatogenic activity was noted at 4 weeks, and complete spermatogenesis, with maximum semen production, occurred after 6 weeks. There was evidence that a successful rejuvenation of the testes requires a period of complete quiescence.
WOODARD ET AL.
218
RESULTS
In Experiment 1, only 16% of the birds in groups 4 and 5 had terminated semen production after 8 weeks on 50% of full feed without a concurrent reduction in photoperiod (Figure 1). After completion of their periods of feed restriction, the average semen volumes of birds in groups 4 and 5 that remained in production had decreased approximately 50% and 78%, respectively. None of the birds in the groups kept under 16 hr light molted during the 8-week
period of feed restriction. After given full access to feed, males in group 4 had the most rapid recovery to full semen production, and had exceeded the level of production attained by groups 5 and 6 by approximately 32%. With one exception, all birds given 8 hr light had terminated semen production after 4 weeks, irrespective of the feed regimen. The exception terminated production one week later. Although semen volumes of birds in groups 1 and 2 decreased at a slightly faster rate than those of birds in group 3, all birds terminated semen production at the same time. After given 16 hr light, most birds in groups 1, 2, and 3 began to produce semen within 5 weeks, and were producing near maximum volumes by the 6th week. Birds given a reduction in daily photoperiod began to molt after 3 weeks. Average biweekly body weights of birds kept under the different feed regimens and photoperiods are shown in Figure 2. Birds in groups 1 and 2 lost approximately 17% and 22%, respectively, of their initial body weights during the first 4 weeks of feed restriction. This compares to only a 6% loss in weight for birds in group 3 that were kept on full feed under 8 hr light. After 6 weeks on full feed, the birds in groups 1 and 2 recovered the weight lost, even though they remained under 8 hr light during most of the recovery period. Birds in groups 4 and 5 that were kept under 16 hr light lost approximately 26% of their initial weight during the 8week period of feed restriction. After 8 weeks on full feed, the birds in groups 4 and 5 still weighed approximately 20% and 10% less, respectively, than their initial weights. Average testicular weights of birds killed at 4, 8, 12, and 16 weeks of test are given in Table 1. Irrespective of the feed restriction regimen used, the testes of males kept under & hr light had regressed significantly (P<.05) in weight by 86% after 4 weeks, and by 90% after 8 weeks. When the birds were returned to 16 hr light, the left testis grew slightly faster than the right one, and their combined average weights exceeded that of the controls (group 6) by 10% and 51%, respectively, after the 4th and 8th weeks. However, these differences were not found to be significant due to the variability among birds within treatments. Although most birds in groups 4 and 5 had not terminated semen production during the 8week period of restricted feeding their testicular weights were regressed 17% and 42%, respectively. After 8 weeks on full feed, the testes of
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Water was withheld for the first three days in all groups but 3 and 6. Birds in groups 1 and 4 were deprived of feed for the first 7 days of the test, then were given 50% of full feed for the next 21 and 49 days, respectively. Birds in groups 2 and 5 were deprived of feed for the first 14 days, then were given 50% of full feed for the next 14 and 42 days, respectively. The amount of feed given each bird during the period of feed restriction was 227 g. This value represented about 50% of their daily requirement as determined from measurements made prior to the start of the test. After completion of their periods of feed restriction, all birds were returned to full feed. Birds in group 3 and 6 had free access to feed throughout the test. One-fourth of the birds from each group was killed at 4, 8, 12, or 16 weeks of test. Individual testes were removed and weighed on a Mettler balance sensitive to the nearest .1 mg. Semen was collected weekly using the method of Burrows and Quinn (1939), and volumes were measured in a graduated syringe to the nearest .01 ml. Body weights were obtained biweekly for all birds prior to slaughter. In Experiment 2 (1975), 40 yearling Broad Breasted White turkey males, 54 weeks of age, were housed under conditions described in Test 1. They were given 8 weeks of 8L:16D per day, followed by 10 weeks of 16L:8D per day. Four birds were killed at the start of the test, and groups of four were killed at biweekly intervals. The left testis from each bird was fixed in Bouin's solution, dehydrated in ethyl alchol, and embedded in paraffin. Later, these testes were sectioned and microscopically examined for stage of spermatogenesis. The data on testes weights were subjected to a one-way analysis of variance and significance among means was determined by Tukey's procedure, described in Steel and Torrie (1960) for determining significance (P<.05) among means.
PHOTOPERIOD AND FEED ON SEMEN PRODUCTION
8 WEEKS
FIG. 1. Average biweekly semen volumes from males kept under different light and feed restriction regimens. Treatments:
Light/day
Feeding
Group 1 Group 2 Group 3 Group 4 Group 5 Group 6
8L:16D(8wk)» 8L:16D(8wk)* 8L:16D(8wk) 16L:8D (cont.)* 16L:8D(cont.)* 16L:8D (cont.)
No feed first No feed first Full feed. No feed first No feed first Full feed.
7 days; 50% full feed 21 days. 14 days; 50% full feed 14 days. 7 days; 50% full feed 49 days. 14 days; 50% full feed 42 days.
•No water for first 3 days.
males in groups 4 and 5 were 31% heavier than those of the controls (group 6), but still 25% lighter than the average weights of males in groups 1, 2, and 3. In Experiment 2, four birds were killed every 2 weeks over an 18-week period; their testicular weights are shown in Figure 3. The testes of males exposed for 4 and 8 weeks of 8 hr light per day had regressed 73% and 89%, respectively, from their initial weights. When the birds were returned to 16 hr light, their testes reached near maximum growth by the 6th week of exposure. This weight was approximately 30% greater than that of the initial weight. Semen volumes declined sharply soon after birds were given 8 hr light. Semen was collected from only two of the 28 birds sampled after 4 weeks of test, and that only in trace amounts. When given 16 hr light, birds reached sexual maturity after 5 weeks, and were producing near maximum volumes by the 6th week. Microscopic examination revealed marked differences in size and development to the seminiferous tubules of testes removed after 2
weeks of exposure to nonstimulatory light. Most tubules contained spermatozoa in their lumens. After 4 weeks of exposure to 8 hr light, most tubules were markedly reduced in size, with a spermatogenetically inactive germinal epithelium. After 8 weeks, the seminiferous tubules were very small, with conspicious amounts of interstitial tissue around them. After the birds were returned to 16 hr light, most of the seminiferous tubules still showed some regression after the 4th week of exposure; but by the 6th week, lumens of most tubules contained many spermatozoa.
DISCUSSION The feed restriction regimens used in our study were not of sufficient magnitude or duration to cause termination of semen production in 54-week old sexually active birds kept under 16 hr light. The size and function of the testes closely approached termination of semen production. This was especially indicated for those males in group 5 that had the greatest loss in
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219
WOODARD ET AL.
220
18.0 -
..-H
"3 I 7.0 "V*--...
••
*—• 6 ~~'•
*
*-•
~ i6.o£\v O 15.0
8 WEEKS
16
FIG. 2. Average biweekly body weights of males kept under different light and feed restriction regimens Treatments:
Light/day
Feeding regimen
Group Group Group Group Group Group
8L:16D(8 wk)* 8L:16D(8wk)* 8L:16D(8 wk) 16L:8D (cont.)* 16L:8D (cont.)* 16L:8D (cont.)
No feed first No feed first Full feed. No feed first No feed first Full feed.
1 2 3 4 5 6
7 days; 50% full feed 21 days. 14 days; 50% full feed 14 days. 7 days; 50% full feed 49 days. 14 days; 50% full feed 42 days.
*No water for first 3 days. testicular size a n d function. It is q u e s t i o n a b l e , however, t h a n an extension of t h e period of feed restriction given t o males in g r o u p 5 w o u l d have eventually resulted in their t e r m i n a t i o n of semen p r o d u c t i o n . Krueger and co-workers ( 1 9 7 7 ) f o u n d t h a t males, given a daily feed re-
striction of 50% of full feed starting w h e n t h e birds were 18 weeks of age, p r o d u c e d favorable volumes of semen from 32 t o 6 2 weeks of age, even t h o u g h t h e birds were a b o u t 30% ligher in weight t h a n c o m p a r a b l e birds allowed full feed. T h e relationship b e t w e e n size of t h e testes
TABLE 1. Average combined testes weight (g) of birds kept under different light and feed restriction regimens Photoperiod (16L:8D)
Photoperiod (8L:16D)' Groups 3
Groups
(wk)
l2
2
3
4
5
6
4 8 12 16
4.4 C 3.9C 26.1 a 43.4 a
3.0C 3.4= 30.6 a 44.5 a
4.2C 4.2C 34.6 a 46.6 a
16.2abc 18.7 a b 30.4 a 37.0 a
22.4 a b 13.2 b c 33.2 a 29.7 a
30.6 a 24.6 a 31.6 a 22.7 a
' ' Values in the same row having different letters are significantly different (P<.05). Birds in groups 1, 2, and 3 were given stimulatory light (16L:8D) after 8 weeks. Each value represents the average testes weights of 3 bird samples. Group:feeding regimen. 1) No feed 7 days, 50% full feed for 21 days; 2) no feed 14 days, 50% full feed for 14 days; 3) full feed, 4) no feed 7 days, 50% full feed for 49 days; 5) no feed 14 days, 50% full feed for 42 days; and 6) full feed.
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tion in old males. This finding m a y lend credence t o o u r previous study (Woodard et al., 1 9 7 5 ) in which recycled males p r o d u c e d a b o u t 20% m o r e semen during a second 20-week period of semen p r o d u c t i o n t h a n did comparable birds k e p t u n d e r c o n s t a n t s t i m u l a t o r y light.
I
Photoperiod (8L:I6D)
1
Photoperiod ( I 6 L : 8 0 )
<
WEEKS
and persistency of semen p r o d u c t i o n is n o t clearly u n d e r s t o o d . Unlike t h e partridge (Alectoris graced), whose testes u n d e r g o rapid regression after 4 weeks of exposure t o 8 hr light (Woodard et al, 1 9 7 8 ) , t h e t u r k e y requires a b o u t 6 t o 8 weeks t o reach c o m p l e t e testicular quiescence (Wilson et al., 1 9 7 6 ) . In t h e present s t u d y males p r e c o n d i t i o n e d u n d e r 8 hr light, t h e n given 16 hr light, had testes t h a t reached m a x i m u m size after 6 weeks. T h e y were twice as heavy as t h o s e of males in group 6, which were allowed t o remain in c o n t i n u o u s p r o d u c t i o n u n d e r 16 hr light, and 26% heavier t h a n t h e average weights of testes of males in groups 4 and 5. These results are in agreement with those of Wilson et al. ( 1 9 7 6 ) , w h o f o u n d t h a t testes weights of yearling males, at t h e start of t h e second recrudescent period, were nearly twice as heavy as those from comparable birds k e p t in semen p r o d u c t i o n u n d e r c o n s t a n t light regimen of 8 hr light 16 hr darkness per day. T h e increase in size of t h e testes following m o l t m a y a c c o u n t for t h e increase in semen p r o d u c -
REFERENCES Burrows, W. H., and J. P. Quinn, 1939. Artificial insemination of chickens and turkeys, USDA Circ. 525. Krueger, K. K., J. A. Owen, C. E. Krueger, and T. M. Ferguson, 1977. Effect of feed or light restriction during the growing and breeding cycles on the reproductive performance of Broad Breasted White turkey males. Poultry Sci. 56:1566—1574. Ogasawara, F. X., W. O. Wilson, and V. S. Asmundson, 1962. The effect of restricting light during the adolescent period on reproductive performance in turkeys subsequently exposed to 12-, 14- and 20hour days. Poultry Sci. 41:1858-1863. Polley, C. R., R. N. Shoffner, R. E. Burger, and E. L. Johnson, 1962. Light regulation in turkey management. 3. Male reproductive performance. Poultry Sci. 41:1570-1573. Steel, R. G. D., and J. H. Torrie, 1960. Principles and procedures of statistics. McGraw-Hill Book Company, Inc., New York. Swanson, M. H., and D. D. Bell, 1974. Force molting of chickens. II. Methods. University of California Coop. Ext. Bull. AXT-411. Wilson, W. O., F. X. Ogasawara, T. D. Siopes, and A. E. Woodard, 1976. Light management of turkey toms. Archiv. fur geflugelkunde 4:147—151. Woodard, A. E., F. X. Ogasawara, R. L. Snyder, and V. Stinnett, 1975. Effect of forced molting on quantity and quality of semen in turkey breeder males as influenced by diet. Poultry Sci. 54:2094— 2101. Woodard, A. E., R. L. Snyder, and L. Fuqua, 1978. Testicular regression and recovery in the chukar partridge as affected by photoperiod. Poultry Sci. 57:298-300.
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FIG. 3. Average biweekly testes weights (g) and semen volumes (ml) from males cycled under 8 weeks of nonstimulatory (8L:16D) light and 10 weeks of stimulatory (16L:8D) light.