J. Anim Sci.
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J. Anim Sci. 1987. 64:254-260.
© 1987 American Society of Animal Science
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Testicular Development, Daily Sperm Production and Epididymal Sperm Reserves in 15-mo-old Angus and Hereford Bulls: Effects of Bull Strain Plus Dietary Energy

G. H. Coulter, T. D. Carruthers1, R. P. Amann and G. C. Kozub

Research Station, Agriculture Canada, Lethbridge, Alberta T1J 4B1 and Colorado State University2, Fort Collins 80523

Abstract

Bull calves (n = 143) were obtained from two strains of Angus and two strains of Hereford cattle for which replacements were selected on the basis of superior feedlot growth performance on either high- or medium-energy diets. From weaning to slaughter at 15 mo of age, bulls were fed either the high-energy (80% grain + 20% forage) or medium-energy diet (100% forage) corresponding to their strain. Bulls in high-energy diet groups had a greater (P<.05) scrotal circumference at 12 mo, but not 15 mo of age, than bulls in medium-energy diet groups. Compared with Hereford bulls, Angus had greater (P<.01) scrotal circumference (36.1 vs 33.9 cm) and greater (P<.05) paired testes weight (570 vs 464 g) at 15 mo of age. Daily sperm production per gram testicular parenchyma (DSP/g) was affected by strain-diet (P<.01) but not by breed. Bulls in medium-energy diet groups had 12% greater DSP/g than did high-energy diet bulls (17.4 x 106 vs 15.5 x 106). Daily sperm production (DSP) was 9% and 30% greater (P<.01) for medium-energy diet bulls in 1980 (8.2 x 109 vs 7.5 x 109) and 1981 (8.0 x 109 vs 6.2 x 109), respectively, compared with high-energy diet bulls. The effect (P<.01) of breed on DSP was attributed to breed differences in paired testes weight. Bulls in the medium-energy diet groups from weaning to 15 mo of age had 76% greater (P<.01) caput-corpus epididymal sperm reserves for Herefords in 1980 (20.1 x 109 vs 11.4 x 109) and 89% greater caput-corpus epididymal sperm reserves for both breeds in 1981 (18.5 x 109 vs 9.8 x 109) and 52% greater (P<.01) cauda epididymal sperm reserves (13.8 x 109 vs 9.1 x 109) than high-energy diet bulls. Breed did not affect epididymal sperm reserves. Estimated capus-corpus epididymal transit times for medium-energy and high-energy diet bulls were 2.2 and 1.7 d. Thus, the sperm production and reserves of young Angus and Hereford bulls should be greater if bulls are selected and managed on a medium-energy rather than a high-energy diet.

Footnotes

1 Present address: Dept. of Vet. Physiol. Sci., Western College of Vet. Med., Univ. of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 3P7.

2 Anim. Reprod. Lab., Colorado State Univ.






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Copyright © 1987 by the American Society of Animal Science.