ELA and fertility in American Standardbred horses

Summary. We have analysed the effects of ELA alleles and sire‐dam ELA incompatibility on two measures of fertility, gestation length and foaling rate, in American Standardbred horses. Using multivariate statistical methods, we corrected for the effects of confounding factors such as dam and sire age, parity, inbreeding, and sire‐dam kinship. These analyses revealed substantial differences between Standardbred trotters and pacers in the effects of several confounding factors. There appear to be no ELA effects on gestation length in either trotters or pacers. However our results suggest that there may be ELA effects on foaling rate associated with specific dam alleles, with sire‐dam incompatibility, and possibly with specific sire alleles, and that these effects differ between trotters and pacers.