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Freezing Bovine Semen. V. Practicability of Collecting and Freezing a Large Number of Successive Ejaculates^{1, 2,}

Dairy Breeding Research Center, Department of Dairy Science, The Pennsylvania State University, University Park

ABSTRACT

From six to 37 successive ejaculates were collected during 12, 2-hr. depletion trials with eight dairy bulls, and used to investigate (a) the proportion of ejaculates acceptable for freezing and (b) the freezability of the acceptable ejaculates. Only ejaculates showing an initial motility of 30% or more and a minimum of 150 million motile spermatozoa were frozen. On this basis, the percentage of culled ejaculates increased as the number of consecutively collected ejaculates increased. Considering the first five consecutive ejaculates, only 6.7% were culled; among the first ten consecutive ejaculates, 11.6% were culled; whereas, among all 257 ejaculates collected, 35.8% were culled. There was no significant difference in the freezability of the acceptable ejaculates among the first five or first ten individual ejaculates, and freezability was comparable with that obtained with ejaculates collected from the same bulls when on a frequency of two or six ejaculates per week. Beyond the tenth ejaculate, freezability was generally, but not significantly, poorer and collection of more than ten consecutive ejaculates probably would be of no practical value. Pooling acceptable ejaculates from a depletion trial resulted in freezability comparable to freezing the ejaculates separately. With adequate sexual preparation, the collection of six or seven consecutive ejaculates from a given bull should make available large numbers of sperm at one time, which should freeze satisfactorily.

¹ Authorized for publication on September 9, 1958, as Paper No. 2291 in the Journal Series of the Pennsylvania Agricultural Experiment Station.

² Supported in part by grants from the Pennsylvania State Association of Artificial Breeding Cooperatives.