Bull BSE and Semen Analysis for Predicting Bull Fertility

Introduction

The term “breeding soundness” refers to a bull’s ability to get cows pregnant. Although few bulls are completely sterile (unable to impregnate a female), unless a bull is capable of getting a reasonable number of cows pregnant during a limited breeding season, he is not an efficient breeder. In an unselected population of bulls, 20 to 40% may have reduced fertility.
High reproductive efficiency is the most economically important factor for success in cow-calf enterprises; it has greater economic impact than growth rate, feed efficiency, or carcass quality. Subfertile bulls delay conception, prolong the calving season, reduce calf weaning weights, and increase the number of cows culled due to failure to become pregnant or conceiving late in the breeding season. With multiple sire breeding groups and low bull-to-female ratios, reproductive performance may be adequate, despite the presence of some bulls with poor breeding performance. However, single-sire mating groups and high bull-to-female ratios increase the importance of fertile bulls. [...]