摘要：In the current study, among 420 Holstein cows, the following ratios of κ-casein genotypes were found: 0.25 were AA, 0.52 were AB and 0.23 were BB. Frequencies of alleles A and B were 0.51 and 0.49, respectively. Cows with κ-casein AA and AB genotypes produced 322.72 and 464.73 kg more milk per year compared to cows of casein BB genotype (P<0.05), respectively. There were no significant differences in the amount of milk produced by cows of AA and AB casein genotypes. There were no statistically significant differences in overall yields (kilograms per year) of milk fat and milk protein between κ-casein genotypes of cows. In contrast, milk from genotype BB cows contained a significantly (P<0.05) higher percentage of milk fat compared to the milks of casein genotypes AA and AB. In spite of the different κ-casein genotypes having a significant influence on milk yield and fat content, heritability estimations showed that all three genotypes were of medium heritability, and heritability did not differ significantly between them. Variability values (of examined traits) were stable and large enough to ensure selection gains in future generations.
