Associations of bovine blood and milk polymorphisms with lactation traits: Holsteins.

First lactation milk yield and percentages of fat, solids-not-fat, and protein were analyzed to determine the possible relationships between 14 polymorphic loci and production in Holstein cows. The polymorphic systems examined were blood groups (A, B, C, F, J, L, M, S, and Z), serum transferrin, and milk proteins (beta-lactoglobulin, alpha s1-casein, beta-casein, and kappa-casein). Several statistical models were utilized. Although results differed according to the analysis conducted, in general, no system had a significant association with first lactation milk yield expressed as a herdmate deviation. Most striking were the relationships between milk protein polymorphisms and percent solids-not-fat and protein deviations; beta-casein and kappa-casein alleles had statistically significant associations with these traits. The F system was significant for percent fat deviations, whereas J x L system interactions were significant for all traits. Degree of heterozygosity over the 14 systems was positively associated with percent protein deviations.