Genetics of Milk Protein Polymorphism and its Relation to Milk Yield Traits in Holstein Cows


Abstract: The distribution and types of \alpha-s_1-casein, \beta-lactoglobulin, \beta-casein and \kappa-casein in Holstein cattle were identified. It was determined that the frequencies of \alpha-s_1-casein were 0.958 and 0.042 for \alpha-s_1-Ka^B and \alpha-s_1-Ka^C; \beta-lactoglobulin, 0.516 and 0.484 for \beta-lgn^A and \beta-lgn^B; \beta-casein, 0.995 and 0.005 for \beta-Ka^A and \beta-Ka^B; and \kappa-casein, 0.677 and 0.323 for \kappa-Ka^A and \kappa-Ka^B, respectively. The differences between the empirical and theoretical distributions of the \alpha-s_1-casein, \beta-lactoglobulin, \beta-casein and \kappa-casein genotypes were not significant. The effects of the \alpha-s_1-casein, \beta-casein and \kappa-casein types on milk yield traits were not significant, while the effects of the \beta-lactoglobulin types were significant (p<0.05). \beta-Lgn^AB type cows produced the highest 2x-ME-305 daily milk yields. The effects of \alpha-s_1-casein types on the length of the lactation period were not significant, while the effects of the \beta-lactoglobulin, \beta-casein and \kappa-casein types were significant (P<0.05).

Keywords: Holstein cattle, Milk Protein Polymorphism \alpha-s_1-casein, \beta-lactoglobulin, \beta-casein and \kappa-casein

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