关键词: 中国荷斯坦牛, LYZ基因, PCR-SSCP, 多态性, 体细胞评分, 305 d产奶量, 乳房炎抗性

Abstract:

【Objective】 The polymorphism of coding region of LYZ gene and its correlation with somatic cell score (SCS) and 305 d milk yield in Chinese Holstein were analyzed for the purpose of providing molecular markers in the marker-assisted selections (MAS) to accelerate the disease-resistant breeding progress in Chinese Holstein .【Method】 The polymorphism of LYZ gene was detected by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique in 610 Chinese Holstein cattle from 30 bull families. The associations between polymorphic sites of LYZ gene and SCS and 305 d milk yield were analyzed by the least square mean analysis. 【Result】 The 115(T＞G)mutation site was found in the exon1, and the mutation resulted in an amino acid change of Arg→Leu, for the polymorphic site, three genotypes (TT, TG and GG) were found in 610 Chinese Holstein by PCR-SSCP,and the frequency of TT, TG and GG genotypes was 0.270, 0.508 and 0.222, respectively. Chi-square tested showed Chinese Holstein was not in Hardy-Weinberg equilibrium at the site. Least square mean of SCS for GG genotype was highly and significantly lower than that for TT (P＜0.01), and significantly lower than TG genotype (P＜0.05). Least square mean of 305 d milk yield for GG genotype was greatly and significantly higher than that for TT (P＜0.01), and significantly higher than TG genotype (P＜0.05).【Conclusion】 GG genotype at 115(T＞G)site had a great genetic effect on SCS and 305 d milk yield in Chinese Holstein, which can be used as a candidate marker for mastitis resistance selection in dairy cattle.

Key words: Chinese Holstein, LYZ gene, PCR-SSCP, polymorphism, SCS, 305 d milk yield, mastitis resistance