Abstract：Abstract Milk fat is an important part of milk. The main feature of yak (Bos grunniens) milk is high fat rate. Diacylglycerol acyltransferase 2 (DGAT2) plays an important role in triacylglyceride synthesis for the milk and is an important candidate gene for milk fat traits. In this study, the polymorphism of DGAT2 gene in Gannan yak, Tianzhu white yak and Datong yak were detected with polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP), and the effects of mutations on milk quality traits were analyzed in Gannan yak. The results showed that 4 SNPs were identified, including c.613-214 A＞G and c.613-337 C＞A in intron5 and c.787＋616 G＞A and c.787＋691 T＞G in intron6 which led to six alleles (A1, B1, C1 in intron5 and A2, B2, C2 in intron6) and two regions were moderate polymorphism in yak populations. Seven haplotypes were found and 4 SNPs were linked but closed to linkage equilibrium between intron5 and intron6 of yak DGAT2 gene. In intron5 of Gannan yak DGAT2 gene, individuals possessing the allele B1 had higher milk fat rate than those no- possessing in second parity yaks (P＜0.05). In intron6 of Gannan yak DGAT2 gene, individuals with alleles A2 showed higher milk fat rate and total solid content than those no-possessing and significant effects were also found in second parity yak (P＜0.05), which indicated that selecting those yaks with allele A2 had the tendency of increasing the milk fat rate and total solid content in offspring groups. The second parity yaks with genotype A2C2 showed higher protein rate than those with genotypes A2C2 and B2B2 (P＜0.05). Gannan yak with haplotype combinations H1H3 had the higher milk fat quality traits than others. The mutations in intron5 and intron6 might be used as genetic markers to improve milk quality traits in Gannan yak. This study has accumulated candidate genes of molecular genetic research data for Yak milk traits.
