allelic polymorphism of k-casein, β-lactoglobulin and leptin genes and their association with milk production traits in iranian holstein cattle

the purpose of this study was to investigate the polymorphism of k-casein (k-cn), β-lactoglobulin (b-lg) and leptin (lp) genes in iranian holstein cattle by polymerase chain reaction-restriction fragment length polymorphism (pcr-rflp) technique. dna was extracted from blood samples of 139 cows using a modified phenol chloroform method. association between k-cn, b-lg and lp genes’ polymorphism with milk production traits were investigated using mixed procedure of sas software. the frequencies of aa, ab and bb genotypes for k-cn (0.72, 0.18 and 0.10), b-lg (0.43, 0.28 and 0.29) and lp (0.24, 0.63 and 0.13) were also calculated. statistical results revealed a significant association between aa and bb genotypes of the k-cn gene with milk production and milk protein percentage, respectively. also, bb genotype of the b-lg gene and aa genotype of the lp gene showed a significant association with protein percentage and milk production (p<0.05), respectively. therefore, it is feasible to improve milk production traits in these herds using the studied genes.