Welper R D, Freeman A E
Department of Animal Science, Iowa State University, Ames 50011.
J Dairy Sci. 1992 May;75(5):1342-8. doi: 10.3168/jds.S0022-0302(92)77885-0.
First lactation milk, fat, protein, and lactose yields and percentage yields were analyzed using a multiple-trait sire model including herd-year-season, sire group, and age of cow as fixed effects. Somatic cell score was fit both as a fixed effect in the model and as an additional dependent variable in two analyses with almost identical results. Variance components were estimated using REML with an expectation-maximization algorithm including sire relationships. Lactose means ranged from 4.84 to 4.97% across three dairy breeds. Data used to estimate variance components were first lactation Holstein records collected from 1986 to 1988 from 5246 daughters of 392 AI sires. Heritability estimates were .30, .29, .27, and .26 for milk, fat, protein, and lactose yields; .45, .47, and .53 for fat, protein, and lactose percentage yields; and .16 for somatic cell score. Genetic correlations of lactose percentage with milk, fat, protein, fat and protein percentages, and somatic cell score were -.30, -.16, -.21, .10, .29, and -.11, respectively, and phenotypic correlations were -.08, -.02, .01, .11, .29, and -.15.
使用多性状父系模型分析头胎泌乳的产奶量、脂肪、蛋白质和乳糖产量及百分比产量，该模型将牛群-年份-季节、父系组和奶牛年龄作为固定效应。体细胞评分在模型中既作为固定效应，又在两项分析中作为额外的因变量，结果几乎相同。使用带有期望最大化算法（包括父系关系）的REML估计方差分量。三个奶牛品种的乳糖均值在4.84%至4.97%之间。用于估计方差分量的数据是1986年至1988年从392头人工授精公牛的5246头女儿那里收集的头胎荷斯坦奶牛记录。牛奶、脂肪、蛋白质和乳糖产量的遗传力估计值分别为0.30、0.29、0.27和0.26；脂肪、蛋白质和乳糖百分比产量的遗传力估计值分别为0.45、0.47和0.53；体细胞评分的遗传力估计值为0.16。乳糖百分比与牛奶、脂肪、蛋白质、脂肪和蛋白质百分比以及体细胞评分的遗传相关性分别为-0.30、-0.16、-0.21、0.10、0.29和-0.11，表型相关性分别为-0.08、-0.02、0.01、0.11、0.29和-0.15。
