J. Anim Sci.
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J. Anim Sci. 1986. 63:579-585.
© 1986 American Society of Animal Science
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Effect of Energy Intake after Weaning on the Sexual Development of Beef Bulls. II. Age at First Mating, Age at Puberty, Testosterone and Scrotal Circumference1,2,

R. J. Pruitt3, L. R. Corah, J. S. Stevenson and G. H. Kiracofe

Kansas State University, Manhattan 66506

Abstract

Simmental and Hereford bulls were individually fed varying levels of the same diet to determine the effect of energy intake after weaning on rate of sexual development. For 200 d, 29 Simmentals were fed an average of 14.6, 19.2 or 23.8 Mcal and 27 Herefords were fed 13.4, 17.5 or 22.2 Mcal metabolizable energy per bull daily. Higher energy did not hasten sexual development, as measured by serum testosterone, age at first mating or age at puberty. As energy level increased, weight at puberty increased (P<.05) for both breeds, and scrotal circumference at puberty increased (P<.05) for Simmentals. When adjusted for breed and energy level, bulls that were heavier at 1 yr of age had larger scrotal circumference (P<.05) and were younger at puberty (P<.01). Bulls that had higher serum testosterone at 1 yr of age reached puberty earlier (P<.01). At a constant age there was no relationship between testosterone and scrotal circumference. Although higher levels of energy increased scrotal circumference of Simmentals, it did not hasten sexual development for either breed.

Footnotes

1 Contribution 86-107-J, Dept. of Anim. Sci. and Ind., Kansas Agr. Exp. Sta., Manhattan 66506.

2 The authors thank Margo Heekin, research assistant, for help in data collection.

3 Present address: Dept. of Anim. and Range Sci., South Dakota State Univ., Brookings, SD 57007.






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Copyright © 1986 by the American Society of Animal Science.