[Polymorphism of bovine TNF-a gene and its association with mastitis in Chinese Holstein cows].

Four hundred and seven Chinese Holstein cows were chosen and divided into 2 groups (healthy group (317), sub-clinical and clinical group (100)) to investigate variation in bovine Tumor necrosis factor-alpha (TNF-a) gene and analyze their associations with mastitis. By PCR-RFLP and CRS-RFLP analyses, three polymorphic sites were detected, with one G→A mutation at 39 bp in exon2 and one C→T mutation at 293 bp in exon4, and C→G mutation in 5´UTR. The three polymorphic sites were able to be cut by DraⅠ, AfaⅠ, and DdeⅠ restriction enzymes respectively, and the DraⅠlocus was Create Restriction Enzyme Cutting Site. Chi-square analysis suggested that the three polymorphic sites did not reach Hardy-Weinberg equilibrium (P<0.05). Least square linear model (LSM) analysis indicated that the DraⅠ, AfaⅠ, and DdeⅠloci of TNF-a gene were associated with somatic cell score (SCS) (P<0.05). Genotype AA in DraⅠlocus and BB in AfaⅠlocus showed significantly higher SCS (P<0.05) and genotype AB in DdeⅠlocus showed significantly lower SCS than AA and BB genotypes in the population tested (P<0.05). This suggested that genotypes BB in DraⅠloci, AA in AfaⅠloci, and AB in DdeⅠloci can be used as candidate markers for mastitis resistance selection in dairy cattle.