Relationships Between Milk Protein Polymorphisms and Major Milk Constituents in Holstein-Friesian Cows

Abstract

Milk samples from 1,908 Holstein Friesian cows were phenotyped for genetic variants of asl-casein, /3-casein, t~-casein, and /3-1actoglobulin. The relationships between milk protein polymorphism and test day milk yield and composition were investigated. After adjustments were made for environmental effects of herd, parity number, month of test, stage of lactation, age of sample at testing, and somatic cell count, milk protein phenotypes were found to be associated with milk yield ; concentrations in fat, protein, casein, and whey protein; and proportion of casein in protein.