Apparent heterozygote excess at the amylase I locus in cattle

Abstract

SUMMARYThe amylase (Am I) genotypes have been determined in sera from 834 cows comprising 562 Friesians, 77 Ayrshires, 106 Guernseys, 62 Jerseys and 27 crossbred cows. All of these cows had completed their third lactation and many were much older. There was a highly significant excess of heterozygotes at the Am I locus. This excess of heterozygotes was highest in high-yielding Friesian herds and there was a significant correlation between percentage heterozygotes and herd yield in the Friesians.