The Impact of Kappa Casein Gene Polymorphism on Milk Components and Other Productive Performance Traits of Chinese Holstein Cattle

Polymorphism of kappa casein gene (κ-cn) at exon 5 in 259 chinese holstein cattle was investigated using polymerase chain reaction-single strand conformation (pcrsscp) technique, to verify its effect on milk composition (fat, protein, lactose, total solids (ts) and solids not fat (snf) content and influence of other factors such as parity and season of calving; aiming at utilizing it as a genetic aid in selection to improve the quality of production of this herd. a 218 bp fragment containing exon 1v of kappa casein gene was amplified by pcr and sscp was applied to identify the structural gene polymorphism of κ-cn. general linear model (glm) was used to analyze differences between genotypes. the results indicated that κ-cn genotypes significantly (p<0.05) affected fat, protein and lactose content. but it had no effect (p>0.05) on ts and snf. however, cows with genotype tt showed higher fat and protein contents (3.89 and 3.50%, respectively) than those of genotypes cc and tc (3.62 and 3.66% for fat; 3.35 and 3.36 % for protein, respectively). except for lactose content; parity had no effect on milk components. also, the results disclosed that season of calving did not affect (p>0.05) milk composition. this study indicated that the κ-cn genetic variants may be used as a genetic aid through increasing the frequency of desired genotypes to improve the quality of production of this herd.