The purpose of this study was to investigate the heritability of somatic cell score (SCS) difference and analyze its changing pattern in Chinese Holstein population in Beijing.Dairy herd improvement (DHI) data of 78 386 Chinese Holstein dairy cows (from 1998 to 2016) obtained from 121 different dairy farms in Beijing were analyzed by the least square method and the SCS difference was calculated using DHI data between the SCSs of the current test-month and the previous test-month.The variance components and heritability of SCS difference were estimated by the linear mixed model and DMU software.The results revealed significant effect (P＜0.01) of herd scale,test year,test season,parity,calving season and current lactation month on SCS difference.The estimated heritability of SCS difference in the current study was (0.054±0.003) for Chinese Holstein cows in Beijing.Among them,the heritability of SCS difference in the first,the second and the third parities were (0.070±0.005),(0.045±0.004),(0.052±0.007),respectively.Since the SCS difference is regarded as a timely simply indicator to detect the occurrence of subclinical mastitis,the estimated heritability of SCS difference might be helpful in the selection practice of resistance to subclinical mastitis in Chinese Holstein cattle.%旨在对北京地区中国荷斯坦牛体细胞评分(SCS)差值变化规律进行探索以及遗传力估计.本研究通过对相邻两个泌乳月SCS差值的计算,利用最小二乘法对北京地区1998 2016年间121个牛场中78 386头中国荷斯坦奶牛DHI数据进行分析,并利用DMU软件和线性混合模型估计SCS差值各方差组分,计算其遗传力.结果表明,场规模、当前测定年、当前测定季节、胎次、产犊季节、当前泌乳月对SCS差值具有极显著性影响(P＜0.01);SCS差值遗传力为(0.054±0.003).其中,一胎、二胎、三胎SCS差值遗传力分别为(0.070±0.005)、(0.045±0.004)、(0.052±0.007).结果表明,SCS差值作为一种实时简易检测隐性乳房炎发生的指标,其遗传力的估计在中国荷斯坦牛抗隐性乳房炎选择中具有重要作用.
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