Animal & Veterinary Sciences, Scottish Agricultural College, Easter Bush, Midlothian, EH25 9RG, United Kingdom.
J Dairy Sci. 2012 Aug;95(8):4618-28. doi: 10.3168/jds.2011-4971.
Genetic parameters were estimated in a joint analysis of log(e)-transformed somatic cell count (TSCC) with either mastitis as a binary trait (MAS) or the number of mastitis cases (NMAS) in Holstein-Friesian cows for the first 3 lactations using a random regression model. In addition, a multi-trait analysis of MAS and NMAS was also implemented. There were 67,175, 30,617, and 16,366 cows with records for TSCC, MAS, and NMAS in lactations 1, 2, and 3, respectively. The frequency of MAS was 14, 20, and 25% in lactations 1, 2, and 3 respectively. The model for TSCC included herd-test-day, age at calving and month of calving, fixed lactation curves nested with calving year groups, and random regressions with Legendre polynomials of order 2 for animal and permanent environmental effects. The model for MAS and NMAS included fixed herd-year-season, age at calving and month of calving, and random animal and permanent environmental effects. All analyses were carried out using Gibbs sampling. Estimates of mean daily heritability averaged over a 305-d lactation were 0.11, 0.14, and 0.15 for TSCC for lactations 1, 2, and 3, respectively. Corresponding heritability estimates for MAS were 0.05, 0.07, and 0.09. The heritabilities for NMAS were similar at 0.06, 0.07, and 0.12, respectively, for lactations 1, 2, and 3. The genetic correlations between lactations 1 and 2, 1 and 3, and 2 and 3 were 0.75, 0.64, and 0.92 for computed 305-d lactation TSCC; 0.55, 0.48, and 0.89 for MAS; and 0.62, 0.42, and 0.85 for NMAS, respectively. The genetic correlations between MAS and TSCC were positive and generally moderate to high. The genetic correlations between computed 305-d lactation TSCC and MAS were 0.53, 0.61, and 0.68 in lactations 1, 2, and 3, respectively. Similar corresponding genetic correlations were obtained between computed 305-d lactation TSCC and NMAS in the respective parities. Mastitis as a binary trait and NMAS in the same lactation were very highly correlated and were genetically the same trait. It is intended that the new parameters will be used in setting up a national evaluation system for the joint analysis of TSCC and MAS.
使用随机回归模型，对荷斯坦弗里生奶牛前 3 个泌乳期的对数转换体细胞计数（TSCC）与乳腺炎的二元性状（MAS）或乳腺炎病例数（NMAS）进行联合分析，估计了遗传参数。此外，还进行了 MAS 和 NMAS 的多性状分析。第 1、2 和 3 泌乳期分别有 67175、30617 和 16366 头奶牛记录了 TSCC、MAS 和 NMAS。第 1、2 和 3 泌乳期 MAS 的频率分别为 14%、20%和 25%。TSCC 的模型包括群体-测奶日、产犊年龄和产犊月份、嵌套在产犊年份组内的固定泌乳曲线以及动物和永久环境效应的 Legendre 多项式阶数 2 的随机回归。MAS 和 NMAS 的模型包括固定的畜群-年-季、产犊年龄和产犊月份以及随机的动物和永久环境效应。所有分析均采用 Gibbs 抽样进行。在 305 天的泌乳期中，平均每日遗传力估计值分别为 0.11、0.14 和 0.15，分别用于第 1、2 和 3 泌乳期的 TSCC。MAS 的相应遗传力估计值分别为 0.05、0.07 和 0.09。NMAS 的遗传力相似，第 1、2 和 3 泌乳期分别为 0.06、0.07 和 0.12。第 1 泌乳期和第 2 泌乳期、第 1 泌乳期和第 3 泌乳期以及第 2 泌乳期和第 3 泌乳期之间的遗传相关性分别为 0.75、0.64 和 0.92，用于计算 305 天的泌乳期 TSCC；0.55、0.48 和 0.89，用于 MAS；0.62、0.42 和 0.85，用于 NMAS。MAS 和 TSCC 之间的遗传相关性为正相关，且通常为中度至高度相关。第 1、2 和 3 泌乳期计算的 305 天泌乳期 TSCC 和 MAS 之间的遗传相关性分别为 0.53、0.61 和 0.68。在各自的胎次中，计算的 305 天泌乳期 TSCC 和 NMAS 之间也获得了类似的遗传相关性。乳腺炎作为二元性状和同一泌乳期的 NMAS 高度相关，并且在遗传上是相同的性状。旨在使用新的参数在全国范围内建立一个联合分析 TSCC 和 MAS 的评估系统。
