Baro J A, Carriedo J A, San Primitivo F
Institute of Cell, Animal and Population Biology, Edinburgh University, Scotland.
J Dairy Sci. 1994 Sep;77(9):2658-62. doi: 10.3168/jds.S0022-0302(94)77207-6.
Records from monthly test days for milk yield, natural log-transformed SCC, and protein percentage of 10,171 records of 3832 Spanish Churra ewes in 24 herds were analyzed to estimate genetic parameters. Heritabilities and genetic and phenotypic correlations for test day records were estimated using multivariate REML with an animal model, accounting for the effects of litter size, test day within herd group, age at lambing, and month in milk. Heritabilities for test day records of milk, log SCC, and protein percentage were .34, .04, and .13, respectively. Genetic correlations of test day measures of SCC with milk yield and protein percentage were -.37 and .37, respectively; phenotypic correlations were -.05 and .19. Considered as a random effect, test day within herd accounted for 28 and 17% of the total variance of test day milk yield and test day SCC, respectively. The correlation between milk yield and SCC because of the test day within herd, the covariation factor, was estimated to be -.16. Results indicate a moderately high heritability for milk yield, a low heritability for SCC, and moderate, negative genetic relationships between measures of SCC in milk and milk yield.
分析了来自24个畜群的3832只西班牙查拉母羊的10171条记录，这些记录包括每月产奶量测试日、自然对数转换后的体细胞计数（SCC）以及蛋白质百分比，以估计遗传参数。使用包含动物模型的多变量约束最大似然法（REML）估计测试日记录的遗传力以及遗传和表型相关性，该模型考虑了产仔数、畜群组内测试日、产羔时年龄和泌乳月份的影响。产奶量、对数SCC和蛋白质百分比的测试日记录的遗传力分别为0.34、0.04和0.13。SCC测试日指标与产奶量和蛋白质百分比的遗传相关性分别为-0.37和0.37；表型相关性分别为-0.05和0.19。作为随机效应，畜群内测试日分别占测试日产奶量和测试日SCC总方差的28%和17%。由于畜群内测试日这一协变因素，产奶量与SCC之间的相关性估计为-0.16。结果表明，产奶量具有中等偏高的遗传力，SCC具有较低的遗传力，且牛奶中SCC指标与产奶量之间存在中等程度的负遗传关系。
