J. Anim Sci.
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J. Anim Sci. 1969. 28:233-239.
© 1969 American Society of Animal Science
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Reproductive Tract of Holstein Bulls from Birth through Puberty1

K. L. Macmillan2 and H. D. Hafs3

Michigan State University, East Lansing

Abstract

Sixty-five Holstein bulls were killed in groups of five at monthly intervals from birth to 12 mo. of age to determine reproductive tract criteria which may be useful estimators of androgen secretion. Testes and seven major portions of the excurrent ducts were weighed and studied histologically. Nucleic acids were determined in testes and seminal vesicles, and fructose and citric acid were determined in seminal vesicles.

Thirteen of these criteria indicated that the period of accelerated reproductive development associated with puberty was terminated by 9 to 10 mo. of age. Some, such as seminal vesicular criteria, which may be more sensitive indicators of androgen secretion, revealed that puberal development may be biphasic. Two periods of accelerated reproductive tract development, one from 2 to 4 mo. and the other from 6 to 9 mo., occurred during periods of rapid increases in plasma LH. The second period of accelerated puberal development was typified by appearance of more obvious external manifestations of puberty and by rapid onset of spermatogenesis.

Footnotes

1 Published with the approval of the Director of the Experiment Station as Paper No. 4413. This research was supported by U.S.P.H.S. grant HD-01374.

2 Present address: New Zealand Dairy Board, Awahuri, Palmerston North, New Zealand.

3 Animal Reproduction Laboratory, Dairy Department.






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Copyright © 1969 by the American Society of Animal Science.