The Relative Usefulness of Combinations of Laboratory Tests for Predicting the Fertility of Bovine Semen

Abstract

Numerous laboratory tests of semen quality have been reported to be correlated with fertility (1, 2-7, 9-12, 14, 15, 17-21). In practice low spermatozoan concentration, low motility, long methylene blue and resazurin reduction times, and a high percentage of abnormal spermatozoa, have been used as bases for rejecting ejaculates which otherwise might have been eonsidered satisfactory for breeding purposes. However, the important considoratioii is not so mueh what eorrelation coefficients are statistically significant and at what level of probability but what combinations of laboratory tests are most useful for prediction purposes, and what percentage of the ejaculates must be discarded to achieve a specified in-crease in the nonreturn rate. To provide some preliminary quantitative estimates of these factors the investigations reported herein were conducted. EXPERIMENTAL PROCEDURE The following measurements were made on each of three ejaculates from each of 53 bulls in the active stud of the New York Artificial Breeders' Cooperative, Inc.: