Observations On the Characteristics of the Semen in Relation to Fertility in the Bull

Abstract

1. The characters of the semen of twenty-one bulls were compared with their fertility as expressed by the service rate—the number of services required for each conception. 2. It was found that, on the basis of the density of the semen, the total number of spermatozoa ejaculated, the motility and change in p H of the semen on incubation at 37° C, the animals could be divided into a higher fertility group with service rates from slightly more than 1·0 to about 3·5, and a lower fertility group with service rates from above 3·5 to ∞. Totally sterile animals could be detected. 3. It is suggested that other factors than the quality of the semen can vary fertility so as to give service rates at different levels from 1·0 to about 3·5. Below a certain level of semen quality fertility appears to be impaired no matter what other factors operate. 4. No relationship could be detected between the percentage of abnormal spermatozoa ejaculated and the service rate. 5. Standards for use in diagnosis of fertility are suggested.