Effect of DGAT1 variants on milk composition traits in Iranian Holstein cattle population

The results from a number of QTL mapping studies recently provided the evidence for quantitative trait loci affecting milk yield and milk fat content localized on bovine chromosome 14 (BTA14) close to DGAT1 gene. DGAT1 gene codes for diacylglycerol-acyltransferase enzyme which plays a main role in the triglyceride synthesis and subsequently the milk composition. A transition mutation in this gene results in substitution of guanine by adenine leading to the substitution of lysine by alanine in diacylglycerol-acyltransferase enzyme. In this study, 398 blood samples were collected from the Holstein dairy farms in Iran. A 411 bp fragment of exon 8 in DGAT1 gene was amplified and the animals were genotyped using RFLP-PCR technique. Three genotypes including KK (36 animals), AA (136 animals) and KA (226 animals) were identified. Frequencies of K and A (mutant type) alleles were estimated to be 0.37 and 0.63, respectively. The effect of DGAT1 gene on FAT (milk fat yield adjusted for two milkings per day, kg), FATP2X 2x (fat content of milk adjusted for two milkings per day, %), EBV (estimated breeding value for fat content of milk, %) and PRO (milk protein content adjusted for 05 days, %) FP occurred highly significant (P<0.001)