荷斯坦牛BoLA-DRB3基因外显子2多态性及其与体细胞评分关系的研究*

采用PCR-RFLP技术用限制性内切酶BstYⅠ对河北省489头荷斯坦母牛和40头荷斯坦公牛BoLA-DRB3基因外显子2的284 bp扩增产物进行多态性分析。荷斯坦母牛经BstYⅠ酶切产生3种基因型AA、AB和BB，其频率分别为0.078、0.380和0.542；荷斯坦公牛经BstYⅠ酶切产生2种基因型AB和BB，其频率分别为0.250和0.750；荷斯坦母牛和公牛在该酶切位点均处于Hardy-Weinberg平衡状态（母牛：χ2=0.45，P=0.799>0.05；公牛：χ2=0.82，P=0.665>0.05）；用最小二乘法分析BoLA-DRB3基因外显子2与荷斯坦母牛体细胞评分(somatic cell score，SCS)的关系，结果表明AA基因型SCS最小二乘均值极显著低于AB基因型所对应的值（P=0.0098<0.01），极显著低于BB基因型所对应的值（P=0.00009<0.0001）；AB基因型SCS最小二乘均值极显著低于BB基因型所对应的值（P=0.0096<0.01）；对乳房炎抗性而言，AA是最有利基因型，BB是最不利基因型。本研究结果可为奶牛乳房炎抗性标记辅助选择提供科学依据。

Polymorphism of Exon 2 of BoLA-DRB3 Gene and Its Relationship with Somatic Cell Score in Holstein Cattle

In the present study, the exon 2 of BoLA-DRB3 gene of 489 Holstein cows and 40 Holstein bulls in Hebei province was amplified and a uniform fragment of 284 bp was obtained. The 284 bp PCR product was digested with restriction endonuclease BstYⅠ, and genetic polymorphism was investigated by PCR-RFLP. Three genotypes (AA, AB and BB) were found in 489 Holstein cows by digesting the PCR product with BstYⅠ, and the frequency of AA, AB and BB genotypes was 0.078, 0.380, 0.542, respectively. Two genotypes (AB and BB) were found in 40 Holstein bulls, and the frequency of AB and BB genotypes was 0.250, 0.750, respectively. The fitnesstest showed that both Holstein cows and bulls were in Hardy-Weinberg equilibrium (cows: χ2 =0.45, P=0.799>0.05; bulls: χ2 =0.82, P=0.665>0.05). The relationship between exon 2 of BoLA-DRB3 gene and somatic cell score (SCS) in Holstein cows was analyzed by least squares linear model. Least squares mean of SCS for AA was significantly lower than that for AB (P=0.0098<0.01) or BB (P=0.00009<0.0001), least squares mean of SCS for AB was significantly lower than that for BB (P=0.0096<0.01). AA was the most favorable genotype, BB was the most unfavorable genotype for mastitis resistance. The information found in the present study is very important for improving mastitis resistance in dairy cattle by marker assisted selection.