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This experiment was conducted to analyze the relationship between polymorphisms of SCD1 gene and the composition of fatty acids in Chinese Holstein.The polymorphism of SCD1 gene was investigated in 323 Chinese Holstein cows from the experimental farm of Yangzhou University using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique, and with a mixed animal model, the effects of polymorphism and haplotypes on the unsaturated fatty acid content and unsaturated index were analyzed.The results showed that three genotypes, AA, AB, BB at SCD1-T762C site and CC, CD, DD at SCD1-C878T site.Meanwhile, the mutation SCD1-T762C was a sense mutation, but mutation SCD1-C878T was missense mutation, causing an amino acid change (Ala293Val).The dominant alleles at SCD1-762 and SCD1-878 sites were respectively A and C, with frequencies of 0.7897 and 0.7835, respectively.The highly significant linkage disequilibrium between SCD1-762 and SCD1-878 was found, and the linkage disequilibrium parameter (r2) was 0.879.The least square analysis indicated that the percentage of mono-unsaturated fatty acid (MUFA) and total unsaturated fatty acid index of genotype TT at SCD1-878 site, genotype BB at SCD1-762 site or genotype BT at SCD1-762-878 site was significantly lower than that of other genotype (P <0.05).The SCD1-A293V substitution has certain genetic effect on milking traits, and its mechanism need further research.