Genetic variability, inbreeding, and reproductive performance in standardbred horses

The relationships between electrophoretically determined genic variability, inbreeding, and reproductive success have been examined for Standardbred horses. There was a statistically significant relationship between foaling and/or conception rate and probability of offspring heterozygosity in Standardbred pacing horses. This relationship could not be explained by inbreeding depression. Inbreeding, at the level observed in Standardbreds, had little or no effect upon reproductive success. Additionally, there was no relationship between the inbreeding coefficient and the observed level of genetic heterozygosity. The results of these analyses suggest a program of a low rate of inbreeding combined with selection for characteristics associated with overall vigor as a management strategy for captive populations.