Abstract: Diacyglycerol acyl-transferase 1 (DGAT1) was considered to be the key enzyme in controlling the synthesis rate of triglycerides. The DGAT1 gene was recently identified,and DGAT1 gene became a strong functional candidate gene for milk fat percentage in cattle. This study used Guizhou Holstein cows as experimental animals,the cow DGAT1 gene was cloned by polymerase chain reaction using PCR primers. PCR-single-strand conformation polymorphism (PCR-SSCP)assay was used to diagnose the DGAT1 exon 8.The results showed that three genotypes were found and the genotypic frequencies of AA, AB and BB were 0.5588,0.3824 and 0.0588,respectively. The gene frequencies of A and B were 0.7549 and 0.2451.The significant association of the gene mutation in DGAT1 exon 8 with 305 days corrected milk yield and milk fat percentage (P<0.05), and had no significant effect on the protein percentage in milk (P>0.05). LSD showed that the cows with AA and AB genotypes had higher tested 305 days corrected milk yield and milk protein percentage than those with BB genotype (P<0.05).The conclusion indicated that the gene mutation in DGAT1 had a great genetic effect on milking traits and could be a useful genetic marker for Guizhou Holstein breeding.

Key words: Guizhou Holstein cows; DGAT1 gene; milk production traits; PCR-SSCP