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Gonadal and Extra Gonadal Sperm Numbers during Reproductive Development of Holstein Bulls¹

Michigan State University, East Lansing

Abstract

Gonadal and extra gonadal sperm numbers were estimated hemocytometrically from tissue homogenates in 65 Holstein bulls between birth and 12 mo. of age. Testicular sperm or terminal stage spermatids were noticed in one 5-mo. old bull. All testicular homogenates from bulls at 8 mo. of age or older contained sperm. Average testicular sperm concentration increased from 4.2 million per gm. parenchyma at 7 mo. of age to 57.3 million per gm. at 12 mo., a value similar to that reported else-where for mature bulls. Thus, Holstein bulls attain their mature rate of spermatogenesis by 1 yr. of age and subsequent increases in sperm production with advancing age are primarily due to increases in testicular weight. In contrast the sperm content of caudae epididymides at 1 yr. is only about 20% of that reported for mature bulls.

¹ Published with the approval of the Director of the Experiment Station as paper No. 4137. This research was supported by U.S.P.H.S. grant HD-01374.

² Present address: New Zealand Dairy Board, Newstead, Hamilton, New Zealand.

³ Animal Reproduction Laboratory, Department of Dairy.