Genetic parameters for the milk coagulation properties and prevalence of noncoagulating milk in Finnish dairy cows

The genetic parameters were estimated for milk coagulation properties and m ilk production traits, and the prevalence of noncoagulating milk in the Fin nish dairy cattle population was investigated. Data were included for 789 F innish Ayrshire cows and 86 Finnish Friesian cows from 51 herds. The animal model used for estimation included fixed effects for parity, stage of lact ation, breed, and herd. Further, effects of milk protein genotypes on pheno typic and genetic variation in the studied traits were examined. Heritabili ty estimates for the milk coagulation properties were moderately high. The kappa-casein B allele was associated with the best phenotypic acid genetic values for curd firmness, and the A and E alleles were associated with the poorest. About 24% of the additive genetic variation in the curd firmness w as due to milk protein polymorphism. About 8% of the Finnish Ayrshire cows in the present study produced noncoagulating milk. Because of the occurrenc e of the noncoagulating milk and a possibly unfavorable genetic trend in th e milk coagulation properties, it would be important to improve these trait s in the Finnish Ayrshire breed. Milk coagulation properties could be impro ved directly by selecting for these traits or indirectly by favoring the ka ppa-casein B allele or by selecting against genetic markers associated with poorly coagulating or noncoagulating milk.