Yahya Mohammadi - Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
Ali Asghar Aslaminejad - Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
MohammadReza Nassiri - Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
Ali Esmailizadeh Koshkoieh - Department of Animal Science, Faculty of Agriculture, university of Shahid Bahonar , Kerman, Iran

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

Holstein cattle, K-casein, β-Lactoglobulin, leptin gene, PCR-RFLP, milk production traits