Polymorphisms of kappa-casein gene and their effects on milk production traits in Holstein, Jersey and Brown Swiss cattle

The objectives of this study were to detect kappa-casein (kappa-CN, CSN3, CASK) gene polymorphisms and to investigate the association between the kappa-CNgene polymorphisms and milk yield and composition in cattle. For this purpose, a total of 365 blood and milk samples were collected from Holstein, Jersey and Brown Swiss cows. Polymorphisms of kappa-CN gene were detected by the PCR and restriction fragment length polymorphism. A776-bp fragment of exon IV was amplified by PCR and digested with HindIII and HaeIII restriction endonuclease to distinguish allele A, B and E. The analysis of associations between kappa-CN genotypes and milk yield and composition were conducted with the use of the general linear model procedure. As a result, allele frequencies were detected as 0.736, 0.357, 0.308 for A allele, 0.186, 0.643, 0.692 for B allele in Holstein, Brown Swiss and Jersey breeds, respectively, and 0.079 for E allele in Holstein. This study also demonstrated the presence of Eallele in Turkish Holstein. Although kappa-CN genotypes were associated with protein and solids-not-fat content of milk in Hostein and Brown Swiss, they were associated with milk fat content in Jerseys (P < 0.05).