Association between milk protein polymorphism and milk production traits in Black and White dairy cattle in Turkey
Milk protein polymorphism such as as1-casein (as1-Cn), b-lactoglobulin (b-Lg), b-casein (b-Cn) and k-casein (k-Cn) of Black and White dairy cattle were investigated in this study. The genetic structure of herd was examined for these loci. At the sametime the relationships between milk protein types and some milk production traits were determined. Milk production traits were chosen as milk yield, average daily milk yield and lactation length. These traits were associated with milk protein types. Genetic variants of milk protein were identified by starch gel electrophoresis containing mercaptoethanol and urea. The allele gene frequencies of A, B, and C of as1-Cn loci and A, B of b-Cn were found to be 0.01; 0.97; 0.02 and 0.95; 0.05 respectively. Furthermore, the allele frequencies of A, B of k-Cn and A, B of b-Lg were found to be 0.68; 0.32 and 0.55; 0.45 respectively. For as1-Cn BB phenotype was found to have
higher milk yield than those of as1-Cn AB and as1-Cn BC phenotypes, and b-Lg AA phenotype was detected to have higher milk yield than those of b-Lg AB and b-Lg BB types but were not statistically important. It was concluded that the genetic structure of the four loci were determined in Black and White cattle, but there was no significant association between the milk protein types and milk production traits in the study.
Key words: Milk protein polymorphism, casein, lactoglobulin, Black and White dairy cattle.