Department of Animal Science, Animal Breeding and Genetics Group, Georg-August-Universität Göttingen, 37075 Göttingen, Germany.
J Dairy Sci. 2013 Sep;96(9):5965-76. doi: 10.3168/jds.2013-7188. Epub 2013 Jul 17.
The aim of this study was to estimate genetic parameters and accuracies of breeding values for milk content traits of individual udder quarters in Brown Swiss cattle. Data of 1,799 phenotyped cows from 40 Swiss dairy herds were analyzed, taking the complete pedigree into account. Fat, protein, lactose, and urea contents, somatic cell score (SCS), and information about hyperkeratosis were available for each udder quarter. The milk of rear udder quarters was found to have significantly higher lactose content and significantly lower fat content than milk of the front udder quarters. The same trend found for fat content was observed for protein content, whereas no differences between the udder quarters were observed for urea content, SCS, or hyperkeratosis. Heritabilities for each udder quarter were in the following ranges: fat content 0.09±0.06 to 0.14±0.06, protein content 0.20±0.09 to 0.33±0.07, lactose content 0.04±0.03 to 0.16±0.07, urea content 0.13±0.07 to 0.22±0.08, SCS 0.18±0.06 to 0.32±0.07, and hyperkeratosis 0.12±0.04 to 0.26±0.05. In our study, hyperkeratosis, protein content, and SCS showed higher heritabilities in the front udder quarters, fat content had higher heritabilities in the rear udder quarters, and no systematic pattern in heritability was observed for lactose content or urea content. Additive genetic correlations between all udder quarters were >0.90 for protein and urea contents, whereas they were remarkably low (<0.60) for SCS. For fat and lactose contents, the genetic correlations between the 2 front or between the 2 rear quarters, respectively, were notably higher than correlations between 1 front and 1 rear quarter, suggesting that the front and the rear udders could be considered as partly genetically different organs. The variability within the udder as such was found to be of low heritability (<0.10) in general, but repeatability was moderate to high for some traits (lactose content: 0.33±0.05, protein content: 0.53±0.05). Some of these findings can be explained by differences in the physiological background of the traits.
本研究旨在估计瑞士褐牛个体乳房各部位牛奶成分性状的遗传参数和育种值的准确性。对来自 40 个瑞士奶牛场的 1799 头已表型测定的奶牛数据进行了分析，考虑了完整的系谱信息。每头乳房各部位均有乳脂、乳蛋白、乳糖、尿素、体细胞评分（SCS）和角化过度信息。后乳房部位的牛奶乳糖含量明显高于前乳房部位，脂肪含量明显低于前乳房部位。乳蛋白含量也呈现出与脂肪含量相同的趋势，而尿素、SCS 和角化过度在乳房各部位之间没有差异。每个乳房部位的遗传力范围如下：乳脂含量为 0.09±0.06 至 0.14±0.06，乳蛋白含量为 0.20±0.09 至 0.33±0.07，乳糖含量为 0.04±0.03 至 0.16±0.07，尿素含量为 0.13±0.07 至 0.22±0.08，SCS 为 0.18±0.06 至 0.32±0.07，角化过度为 0.12±0.04 至 0.26±0.05。在本研究中，前乳房部位的角化过度、蛋白含量和 SCS 具有较高的遗传力，而后乳房部位的脂肪含量具有较高的遗传力，而乳糖含量或尿素含量则没有系统的遗传力模式。所有乳房部位之间的加性遗传相关系数均>0.90，用于蛋白和尿素含量，而 SCS 则显著较低（<0.60）。对于脂肪和乳糖含量，前两个或后两个乳房之间的遗传相关性分别明显高于前一个和后一个乳房之间的相关性，表明前乳房和后乳房可以被认为是部分遗传上不同的器官。乳房内的变异性总体上具有较低的遗传力（<0.10），但对于某些性状具有中等至高的重复性（乳糖含量：0.33±0.05，蛋白含量：0.53±0.05）。这些发现中的一些可以用性状的生理背景差异来解释。
