Selection for fertility on the basis of AI data

Abstract

The present contribution is a review of earlier studies on genetic aspects of bull fertility as measured by non-return rate when used for AI. The conclusions may be summarised as follows. 1. (1) Conception rate and calving interval are determined by the fertility of the bull and the fertility of the cow jointly. One unit of genetic improvement in male fertility is therefore of equal importance to one unit of improvement in female fertility. 2. (2) The heritability of bull fertility, as measured by the non-return rates from a few hundred inseminations, is large enough to provide a basis for efficient selection. The genetic standard deviation is, however, considerably less for male than for female fertility. 3. (3) The genetic correlation between male and female fertility is slight, and the same holds true for the genetic correlation between male fertility and milk production. 4. (4) In the final selection of progeny-tested bulls, due attention should be given to the estimated breeding value of the bull with respect to male fertility as well as to female fertility.