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

¹ Centre for Food and Animal Research, Agriculture and Agri-Food Canada, Ottawa, ON, Canada K1A 0C6
² Department of Animal Sciences, University of Kentucky, Lexington 40546

The -casein, ß-casein, and ß-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 -casein and ß-casein loci had no significant effects on ETA of the bulls for milk, fat, and protein. The effect of ß-lactoglobulin on ETA of protein approached significance. Results suggest that increasing the frequency of the A variant of ß-lactoglobulin in young bulls entering progeny testing improves ETA for protein of the bulls, but the expected improvement is limited.

Key Words: DNA genotyping • milk protein variants • daughter yield deviation • animal model

Submitted on August 4, 1995
Accepted on February 20, 1996

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