Association between milk protein polymorphism and milk production traits in Black and White dairy cattle in Turkey

Abstract

Milk protein polymorphism such as αs1-casein (αs1-Cn), β-lactoglobulin (β-Lg), β-casein (β-Cn) and κ
casein (κ-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 αs1-Cn loci and A, B of β-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 κ-Cn and A, B of β
Lg were found to be 0.68; 0.32 and 0.55; 0.45 respectively. For αs1-Cn BB phenotype was found to have 
higher milk yield than those of αs1-Cn AB and αs1-Cn BC phenotypes, and β-Lg AA phenotype was 
detected to have higher milk yield than those of β-Lg AB and β-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.