Association Between Milk Protein Genetic Variants and Genetic Values of Canadian Holstein Bulls for Milk Yield Traits

Abstract

The kappa-casein, beta-casein, and beta-lactoglobulin genotypes of 566 bulls were identified by polymerase chain reaction. The associations of these milk protein types with the daughter yield deviations of the 566 bulls for milk, fat, and protein were examined with a mixed model analysis using an animal model. The results suggest that kappa-casein and beta-casein loci had no significant effects on ETA of the bulls for milk, fat, and protein. The effect of beta-lactoglobulin on ETA of protein approached significance. Results suggest that increasing the frequency of the A variant of beta-lactoglobulin in young bulls entering progeny testing improves ETA for protein of the bulls, but the expected improvement is limited.