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Semen Production, Sperm Quality, and Their Heritabilities as Influenced by Selection for Fertility of Frozen-Thawed Semen in the Chicken
Semen Production, Sperm Quality, and Their Heritabilities as Influenced by Selection for Fertility of Frozen-Thawed Semen in the Chicken G. A. ANSAH, J. C. SEGURA, and R. B. BUCKLAND
(Received for publication September 10, 1984) ABSTRACT Ejaculate volume, sperm concentration, and sperm number per ejaculate were measured six times from 8 to 15 months of age, and testes and body weight at 15 months of age, on Generation 9 males of a line of broiler breeders selected for fertility of frozen-thawed semen and those of a randombred control line. Sperm quality (percent normal, percent abnormal, and percent dead sperm) was determined on Generation 10 males at 11 months of age. Selection decreased (P<.01) ejaculate volume and sperm number per ejaculate. The control line had 4.9% more abnormal (P<.05) sperm than the selected line. The differences between the lines for sperm concentration, testes and body weights, and percent dead sperm were not significant (P>.05). The correlation coefficients of fertility of frozen-thawed semen with percent abnormal and percent dead sperm were negative but were positive with percent normal sperm. The heritability and repeatability estimates of ejaculate volume, sperm concentration, and sperm number per ejaculate ranged from .34 to .73 and .33 to .51, respectively. (Key words: semen, selection, frozen-thawed semen, fertility heritability) 1985 Poultry Science 64:1801-1803 INTRODUCTION Positive correlations, as well as lack of correlations, of ejaculate volume and sperm c o n c e n t r a t i o n with fertility have been well d o c u m e n t e d ( S a m p s o n and Warren, 1 9 3 9 ; Cooper and Rowell, 1 9 5 8 ; Soller et al., 1 9 6 5 ; Ansah et al., 1 9 8 0 ) . A n association b e t w e e n morphologically a b n o r m a l sperm and fertility has been reported (Saeki, 1 9 6 1 ; H a y e et al., 1 9 8 1 ) . T h e present s t u d y examined t h e effect of selection for d u r a t i o n of fertility of frozent h a w e d semen o n ejaculate v o l u m e , sperm c o n c e n t r a t i o n , sperm n u m b e r p e r ejaculate, sperm quality (percent n o r m a l , p e r c e n t abnormal, p e r c e n t d e a d ) , and a d u l t b o d y and testes weights. In a d d i t i o n , w e calculated t h e heritability and repeatability estimates of ejaculate volume, sperm c o n c e n t r a t i o n , and sperm n u m b e r per ejaculate as well as t h e relationships of sperm quality with fertility of frozen-thawed semen. MATERIALS AND METHODS Males of a line of broiler breeder chickens selected for d u r a t i o n of fertility of frozent h a w e d semen and of a r a n d o m b r e d control line (Ansah and Buckland, 1 9 8 3 ) were used. A d u l t males were housed in individual cages measuring 30 b y 4 5 b y 5 0 cm at 22 weeks of age and received 15 hr light ( 0 5 0 0 t o 2 0 0 0 h ) . T h e y
were fed a p p r o x i m a t e l y 2 0 7 g of commercial breeding ration (18% protein, 2 7 5 0 kcal m e tabolizable energy/kg) per male o n alternate days. T o s t u d y semen p r o d u c t i o n , semen was collected from Generation 9 males twice per week (Monday and T h u r s d a y ) . During t h e 8 t h , 10th, 1 2 t h , 13th, 14th, and 1 5 t h m o n t h of age, single semen collections w e r e m a d e b y a b d o m i n a l massage (Burrows and Q u i n n , 1937) o n 62 t o 117 selected line and 38 t o 55 c o n t r o l line males. Semen volume was m e a s u r e d and sperm c o n c e n t r a t i o n estimated b y optical density p r o c e d u r e s (Taneja and G o w e , 1 9 6 1 ) . Testes and b o d y weights were m e a s u r e d o n 6 7 selected and 37 c o n t r o l line males at 15 m o n t h s of age. S p e r m quality (percent n o r m a l , p e r c e n t a b n o r m a l , and p e r c e n t dead) was m e a s u r e d o n 4 1 selected line and 37 c o n t r o l line males of t h e g e n e r a t i o n 10 p o p u l a t i o n at 11 m o n t h s o f age. T h e second d a y after an initial ejaculation, semen was collected and smears p r e p a r e d within 2 0 m i n of collection. Vital staining w a s used t o estimate n o r m a l , a b n o r m a l , and dead sperm (Marini and G o o d m a n , 1 9 6 9 ) . Differential c o u n t s were m a d e of 3 0 0 sperm per sample b y each of t w o p e o p l e and t h e average n u m b e r of a b n o r m a l and dead sperm were expressed as percentage of t h e t o t a l n u m b e r of sperm c o u n t e d . Sperm were classified as either
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Downloaded from https://academic.oup.com/ps/article-abstract/64/9/1801/1531737 by Iowa State University user on 23 January 2019
Department of Animal Science, Macdonald College ofMcGill University, Ste. Anne de Bellevue, Quebec, Canada, H9X ICO
ANSAH ET AL.
1802
RESULTS AND DISCUSSION
The selected line used in this study has
significantly higher fertility of frozen-thawed semen than the control line (Ansah and Buckland, 1983). The duration of fertility of frozenthawed semen for Generation 9 was 6.3 days in the selected line and 3.0 days in the control line. For Generation 10, the values were 5.1 and 2.8 days, respectively. The differences between the lines for fertility were significant (P<.01) in both generations. Selection for fertility of frozen-thawed semen over 9 generations decreased (P<.01) ejaculate volume and sperm number per ejaculate but had no effect (P>.05) on sperm concentration (Table 1). Thus, the observed effect of selection on sperm number per ejaculate is due to a reduction in ejaculate volume. These semen production traits declined with age. There were no interactions between line and age for any of the above semen traits, which indicates superiority of the control over the selected line in semen production throughout the production period. The selected line had a higher percentage of normal sperm (P<.05) and a correspondingly lower percentage of abnormal sperm (P<.01) than the control line (Table 1). These results suggest that fertility of frozen-thawed semen may be more dependent upon sperm quality than quantity. There were no differences between the selected and control lines with respect to either body weight or testes weight at 15 months of age (Table 1). The positive correlations of testes weight with ejaculate volume (.31), sperm concentration (.28), and number of sperm per ejaculate (.35) at 15 months of age were low
TABLE 1. Least squares means and standard errors and the heritability and repeatability estimates of semen traits Heritability
Least squares means ± SE Parameter Ejaculate volume, ml Sperm concentration, 1 X 10 9 cells/ml Sperm number/ejaculate, 1 X 1 0 ' cells Body weight, kg Testes weight, g % Normal sperm % Abnormal sperm % Dead sperm
Selected .47 ± .01** 7.58 + .04 3.71 4.54 37.40 89.1 5.6 5.3
± .07* ± .06 ± 1.13 ± 1.5* +1.0** ± .6
'Significant line differences (P<.05). ''Significant line differences (P<.01).
Repeatability
Selected
Control
Selected
Control
.59 ± .01
.34
.64
.35
.48
7.51 ± .01
.37
.65
.33
.50
.54
.73
.42
.51
Control
4.57 ± 4.57 ± 36.62 ± 83.1 ± 10.5 ± 6.5 ±
.08 .09 1.60 1.5 1.0 .6
Downloaded from https://academic.oup.com/ps/article-abstract/64/9/1801/1531737 by Iowa State University user on 23 January 2019
normal (unstained), dead (stained), or morphologically abnormal. Fertility of frozen-thawed semen was determined at 8 months of age in each generation as described by Ansah and Buckland (1983). For Generations 9 and 10, the selected line was produced from 20 sires and 36 dams and 20 sires and 34 dams, respectively, and the control line from 33 and 32 sire-dam-families (parented pairs), respectively. Percentage data were transformed to arcsin / % for the analysis of variance. All data were analyzed using the general linear model procedure of the Statistical Analysis System (SAS, 1979) to test the effects of line, age, and their interaction on the semen production traits, and day and line on sperm quality, testes, and body weights where applicable. Heritability (h 2 ) and repeatability (r) estimates were calculated using the Maximum Likelihood (ML) estimates of variance components (Statistical Analysis System, 1979). Heritability estimates were based on sire plus dam variance components in the selected line and on full-sib covariance in the control line. In both lines, with variance components o\ for individual males and a\ for single samples, repeatability was defined as r = a 2 / ( a ^ + a\). Correlations between testes weight and semen traits were computed after adjustment for significant (P<.05) line Cucct. Correlations between sperm quality and fertility parameters were computed within line.
SEMEN TRAITS AND FERTILITY
REFERENCES Ansah, G. A., and R. B. Buckland, 1983. Eight generations of selection for duration of fertility of frozen-thawed semen in the chicken. Poultry Sci. 62:1529-1538. Ansah, G. A., R. B. Buckland, D. C. Crober, and A. E. Sefton, 1980. Artificial insemination of indi-
vidually caged broiler breeders. II. The relationships of juvenile male traits with subsequent reproductive traits. Poultry Sci. 59:1912— 1917. Burrows, W. H., and J. P. Quinn, 1937. Collection of spermatozoa from domestic fowl and turkey. Poultry Sci. 16:19-24. Cooper, D. M., and J. G. Rowell, 1958. Relations between fertility, embryonic survival, and some semen characteristics in the chicken. Poultry Sci. 37:699-707. Haye, U., A. van Voorst, and R. Pit, 1981. Selection for sperm quality in Plymouth Rocks. Reprod. Nutr. Dev. 21:1067-1075. Marini, P. J., and B. L. Goodman, 1969. Semen characteristics as influenced by selection for divergent growth rate in Chickens. Poultry Sci. 48:859-864. Saeki, Y., 1961. Crooked-necked spermatozoa in relation to low fertility in the artificial insemination of fowl. Poultry Sci. 39:1354-1361. Sampson, F. R., and D. G. Warren, 1939. Density suspension and morphology of sperms in relation to fertility in the fowl. Poultry Sci. 18:301-307. Siegel, P. B., 1963. Selection for body weight at eight weeks of age. II. Correlated responses of feathering, body weights, and reproductive characteristics. Poultry Sci. 42:896-905. Soller, M., N. Snapir, and H. Schindler, 1965. Heritability of semen quality, concentration and motility in White Rock roosters, and their genetic correlation with rate of gain. Poultry Sci. 44: 1527-1529. Statistical Analysis System, 1979. Stat. Anal. Syst. Inst., Cary, NC. Taneja, G. C , and R. S. Gowe, 1961. Spermatozoa concentration in the semen of two breeds of fowl by three different methods. Poultry Sci. 40: 608-615.
Downloaded from https://academic.oup.com/ps/article-abstract/64/9/1801/1531737 by Iowa State University user on 23 January 2019
b u t significant ( P < . 0 1 ) . T h e correlation coefficient of p e r c e n t n o r m a l , p e r c e n t abnormal, and p e r c e n t dead sperm w i t h d u r a t i o n of fertility of frozen-thawed semen in t h e selected line (.26, —.20, —.17) were n o t significant ( P > . 0 5 ) , while in t h e c o n t r o l line ( . 5 3 , —.56, —.37) t h e y were significant ( P < . 0 5 ) . This difference in correlat i o n coefficients in t h e t w o lines m a y b e d u e t o smaller variation for these traits within t h e selected line t h a n in t h e c o n t r o l line. Heritability and repeatability estimates (Table 1) of t h e semen traits were lower in t h e selected line t h a n in t h e c o n t r o l line. Differences in t h e heritability estimates b e t w e e n lines suggest selection m a y have resulted in a decrease in t h e additive genetic variance. Heritability estimates of ejaculate volume and sperm c o n c e n t r a t i o n were higher t h a n t h e estimates r e p o r t e d b y Siegel ( 1 9 6 3 ) b u t similar t o those r e p o r t e d b y Soller et al. ( 1 9 6 5 ) . These results indicate t h a t w i t h selection for improved fertility of frozen-thawed semen it m a y be necessary t o also select for semen volume t o hold this trait c o n s t a n t .
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(Received for publication September 10, 1984) ABSTRACT Ejaculate volume, sperm concentration, and sperm number per ejaculate were measured six times from 8 to 15 months of age, and testes and body weight at 15 months of age, on Generation 9 males of a line of broiler breeders selected for fertility of frozen-thawed semen and those of a randombred control line. Sperm quality (percent normal, percent abnormal, and percent dead sperm) was determined on Generation 10 males at 11 months of age. Selection decreased (P<.01) ejaculate volume and sperm number per ejaculate. The control line had 4.9% more abnormal (P<.05) sperm than the selected line. The differences between the lines for sperm concentration, testes and body weights, and percent dead sperm were not significant (P>.05). The correlation coefficients of fertility of frozen-thawed semen with percent abnormal and percent dead sperm were negative but were positive with percent normal sperm. The heritability and repeatability estimates of ejaculate volume, sperm concentration, and sperm number per ejaculate ranged from .34 to .73 and .33 to .51, respectively. (Key words: semen, selection, frozen-thawed semen, fertility heritability) 1985 Poultry Science 64:1801-1803 INTRODUCTION Positive correlations, as well as lack of correlations, of ejaculate volume and sperm c o n c e n t r a t i o n with fertility have been well d o c u m e n t e d ( S a m p s o n and Warren, 1 9 3 9 ; Cooper and Rowell, 1 9 5 8 ; Soller et al., 1 9 6 5 ; Ansah et al., 1 9 8 0 ) . A n association b e t w e e n morphologically a b n o r m a l sperm and fertility has been reported (Saeki, 1 9 6 1 ; H a y e et al., 1 9 8 1 ) . T h e present s t u d y examined t h e effect of selection for d u r a t i o n of fertility of frozent h a w e d semen o n ejaculate v o l u m e , sperm c o n c e n t r a t i o n , sperm n u m b e r p e r ejaculate, sperm quality (percent n o r m a l , p e r c e n t abnormal, p e r c e n t d e a d ) , and a d u l t b o d y and testes weights. In a d d i t i o n , w e calculated t h e heritability and repeatability estimates of ejaculate volume, sperm c o n c e n t r a t i o n , and sperm n u m b e r per ejaculate as well as t h e relationships of sperm quality with fertility of frozen-thawed semen. MATERIALS AND METHODS Males of a line of broiler breeder chickens selected for d u r a t i o n of fertility of frozent h a w e d semen and of a r a n d o m b r e d control line (Ansah and Buckland, 1 9 8 3 ) were used. A d u l t males were housed in individual cages measuring 30 b y 4 5 b y 5 0 cm at 22 weeks of age and received 15 hr light ( 0 5 0 0 t o 2 0 0 0 h ) . T h e y
were fed a p p r o x i m a t e l y 2 0 7 g of commercial breeding ration (18% protein, 2 7 5 0 kcal m e tabolizable energy/kg) per male o n alternate days. T o s t u d y semen p r o d u c t i o n , semen was collected from Generation 9 males twice per week (Monday and T h u r s d a y ) . During t h e 8 t h , 10th, 1 2 t h , 13th, 14th, and 1 5 t h m o n t h of age, single semen collections w e r e m a d e b y a b d o m i n a l massage (Burrows and Q u i n n , 1937) o n 62 t o 117 selected line and 38 t o 55 c o n t r o l line males. Semen volume was m e a s u r e d and sperm c o n c e n t r a t i o n estimated b y optical density p r o c e d u r e s (Taneja and G o w e , 1 9 6 1 ) . Testes and b o d y weights were m e a s u r e d o n 6 7 selected and 37 c o n t r o l line males at 15 m o n t h s of age. S p e r m quality (percent n o r m a l , p e r c e n t a b n o r m a l , and p e r c e n t dead) was m e a s u r e d o n 4 1 selected line and 37 c o n t r o l line males of t h e g e n e r a t i o n 10 p o p u l a t i o n at 11 m o n t h s o f age. T h e second d a y after an initial ejaculation, semen was collected and smears p r e p a r e d within 2 0 m i n of collection. Vital staining w a s used t o estimate n o r m a l , a b n o r m a l , and dead sperm (Marini and G o o d m a n , 1 9 6 9 ) . Differential c o u n t s were m a d e of 3 0 0 sperm per sample b y each of t w o p e o p l e and t h e average n u m b e r of a b n o r m a l and dead sperm were expressed as percentage of t h e t o t a l n u m b e r of sperm c o u n t e d . Sperm were classified as either
1801
Downloaded from https://academic.oup.com/ps/article-abstract/64/9/1801/1531737 by Iowa State University user on 23 January 2019
Department of Animal Science, Macdonald College ofMcGill University, Ste. Anne de Bellevue, Quebec, Canada, H9X ICO
ANSAH ET AL.
1802
RESULTS AND DISCUSSION
The selected line used in this study has
significantly higher fertility of frozen-thawed semen than the control line (Ansah and Buckland, 1983). The duration of fertility of frozenthawed semen for Generation 9 was 6.3 days in the selected line and 3.0 days in the control line. For Generation 10, the values were 5.1 and 2.8 days, respectively. The differences between the lines for fertility were significant (P<.01) in both generations. Selection for fertility of frozen-thawed semen over 9 generations decreased (P<.01) ejaculate volume and sperm number per ejaculate but had no effect (P>.05) on sperm concentration (Table 1). Thus, the observed effect of selection on sperm number per ejaculate is due to a reduction in ejaculate volume. These semen production traits declined with age. There were no interactions between line and age for any of the above semen traits, which indicates superiority of the control over the selected line in semen production throughout the production period. The selected line had a higher percentage of normal sperm (P<.05) and a correspondingly lower percentage of abnormal sperm (P<.01) than the control line (Table 1). These results suggest that fertility of frozen-thawed semen may be more dependent upon sperm quality than quantity. There were no differences between the selected and control lines with respect to either body weight or testes weight at 15 months of age (Table 1). The positive correlations of testes weight with ejaculate volume (.31), sperm concentration (.28), and number of sperm per ejaculate (.35) at 15 months of age were low
TABLE 1. Least squares means and standard errors and the heritability and repeatability estimates of semen traits Heritability
Least squares means ± SE Parameter Ejaculate volume, ml Sperm concentration, 1 X 10 9 cells/ml Sperm number/ejaculate, 1 X 1 0 ' cells Body weight, kg Testes weight, g % Normal sperm % Abnormal sperm % Dead sperm
Selected .47 ± .01** 7.58 + .04 3.71 4.54 37.40 89.1 5.6 5.3
± .07* ± .06 ± 1.13 ± 1.5* +1.0** ± .6
'Significant line differences (P<.05). ''Significant line differences (P<.01).
Repeatability
Selected
Control
Selected
Control
.59 ± .01
.34
.64
.35
.48
7.51 ± .01
.37
.65
.33
.50
.54
.73
.42
.51
Control
4.57 ± 4.57 ± 36.62 ± 83.1 ± 10.5 ± 6.5 ±
.08 .09 1.60 1.5 1.0 .6
Downloaded from https://academic.oup.com/ps/article-abstract/64/9/1801/1531737 by Iowa State University user on 23 January 2019
normal (unstained), dead (stained), or morphologically abnormal. Fertility of frozen-thawed semen was determined at 8 months of age in each generation as described by Ansah and Buckland (1983). For Generations 9 and 10, the selected line was produced from 20 sires and 36 dams and 20 sires and 34 dams, respectively, and the control line from 33 and 32 sire-dam-families (parented pairs), respectively. Percentage data were transformed to arcsin / % for the analysis of variance. All data were analyzed using the general linear model procedure of the Statistical Analysis System (SAS, 1979) to test the effects of line, age, and their interaction on the semen production traits, and day and line on sperm quality, testes, and body weights where applicable. Heritability (h 2 ) and repeatability (r) estimates were calculated using the Maximum Likelihood (ML) estimates of variance components (Statistical Analysis System, 1979). Heritability estimates were based on sire plus dam variance components in the selected line and on full-sib covariance in the control line. In both lines, with variance components o\ for individual males and a\ for single samples, repeatability was defined as r = a 2 / ( a ^ + a\). Correlations between testes weight and semen traits were computed after adjustment for significant (P<.05) line Cucct. Correlations between sperm quality and fertility parameters were computed within line.
SEMEN TRAITS AND FERTILITY
REFERENCES Ansah, G. A., and R. B. Buckland, 1983. Eight generations of selection for duration of fertility of frozen-thawed semen in the chicken. Poultry Sci. 62:1529-1538. Ansah, G. A., R. B. Buckland, D. C. Crober, and A. E. Sefton, 1980. Artificial insemination of indi-
vidually caged broiler breeders. II. The relationships of juvenile male traits with subsequent reproductive traits. Poultry Sci. 59:1912— 1917. Burrows, W. H., and J. P. Quinn, 1937. Collection of spermatozoa from domestic fowl and turkey. Poultry Sci. 16:19-24. Cooper, D. M., and J. G. Rowell, 1958. Relations between fertility, embryonic survival, and some semen characteristics in the chicken. Poultry Sci. 37:699-707. Haye, U., A. van Voorst, and R. Pit, 1981. Selection for sperm quality in Plymouth Rocks. Reprod. Nutr. Dev. 21:1067-1075. Marini, P. J., and B. L. Goodman, 1969. Semen characteristics as influenced by selection for divergent growth rate in Chickens. Poultry Sci. 48:859-864. Saeki, Y., 1961. Crooked-necked spermatozoa in relation to low fertility in the artificial insemination of fowl. Poultry Sci. 39:1354-1361. Sampson, F. R., and D. G. Warren, 1939. Density suspension and morphology of sperms in relation to fertility in the fowl. Poultry Sci. 18:301-307. Siegel, P. B., 1963. Selection for body weight at eight weeks of age. II. Correlated responses of feathering, body weights, and reproductive characteristics. Poultry Sci. 42:896-905. Soller, M., N. Snapir, and H. Schindler, 1965. Heritability of semen quality, concentration and motility in White Rock roosters, and their genetic correlation with rate of gain. Poultry Sci. 44: 1527-1529. Statistical Analysis System, 1979. Stat. Anal. Syst. Inst., Cary, NC. Taneja, G. C , and R. S. Gowe, 1961. Spermatozoa concentration in the semen of two breeds of fowl by three different methods. Poultry Sci. 40: 608-615.
Downloaded from https://academic.oup.com/ps/article-abstract/64/9/1801/1531737 by Iowa State University user on 23 January 2019
b u t significant ( P < . 0 1 ) . T h e correlation coefficient of p e r c e n t n o r m a l , p e r c e n t abnormal, and p e r c e n t dead sperm w i t h d u r a t i o n of fertility of frozen-thawed semen in t h e selected line (.26, —.20, —.17) were n o t significant ( P > . 0 5 ) , while in t h e c o n t r o l line ( . 5 3 , —.56, —.37) t h e y were significant ( P < . 0 5 ) . This difference in correlat i o n coefficients in t h e t w o lines m a y b e d u e t o smaller variation for these traits within t h e selected line t h a n in t h e c o n t r o l line. Heritability and repeatability estimates (Table 1) of t h e semen traits were lower in t h e selected line t h a n in t h e c o n t r o l line. Differences in t h e heritability estimates b e t w e e n lines suggest selection m a y have resulted in a decrease in t h e additive genetic variance. Heritability estimates of ejaculate volume and sperm c o n c e n t r a t i o n were higher t h a n t h e estimates r e p o r t e d b y Siegel ( 1 9 6 3 ) b u t similar t o those r e p o r t e d b y Soller et al. ( 1 9 6 5 ) . These results indicate t h a t w i t h selection for improved fertility of frozen-thawed semen it m a y be necessary t o also select for semen volume t o hold this trait c o n s t a n t .
1803