ORIGINAL RESEARCH: Milk protein polymorphisms in Holstein cattle[dagger]

Milk samples from 203 Holstein cows were phenotyped for genetic variants as1-casein, B-casein, K-casein and B-lactoglobulin using starch-gel electrophoresis. All of the four milk protein loci exhibited polymorphism with allele frequencies of 0.862+/-0.017 for as1-casein B, 0.966+/-0.0009 for B-casein A, 0.712+/-0.0224 for K-casein A and 0.567+/-0.0245 for B-lactoglobulin B. The mean heterozygosity estimated over all the four milk protein loci was 0.3015. Genetic equilibrium was observed among all of the loci investigated, except K-casein. Chi-squared tests revealed that there was no significant linkage among studied milk protein phenotypes.