Boettcher P J, Hansen L B, VanRaden P M, Ernst C A
Department of Animal Science, University of Minnesota, St. Paul 55108.
J Dairy Sci. 1992 Apr;75(4):1127-37. doi: 10.3168/jds.S0022-0302(92)77858-8.
Lactational means of somatic cell score from sample days of primiparous DHI cows were analyzed to compare dairy records processing centers for data properties, to examine effects of age at calving and month of calving on somatic cell score, and to calculate preliminary PTA of sires for somatic cell scores. Five processing centers contributed data but differed substantially with respect to availability of records in progress, DIM on last sample day, and length of time that data were submitted. Highest lactational means of somatic cell score tended to be in short lactations for young cows but in long lactations for older cows. Regions of the country differed substantially for effect of month of calving on lactational means of somatic cell score, but lactational means of somatic cell scores increased with age at calving for all dairy records processing centers. Standardized yields of milk, fat, and protein were included as multiple traits with somatic cell score for analysis. Heritability of somatic cell score was .08 to .16 for individual processing centers and .10 across processing centers. Phenotypic correlations of somatic cell score with yield traits were negative, but genetic correlations were positive. Selection for decreased somatic cell score on a national basis should be possible and would seem advisable to decrease mastitis infections. Response may be slow, however, because of antagonistic genetic relationships with the yield traits, which have great economic importance.
分析了初产奶牛DHI样本日体细胞评分的泌乳期数据，以比较各乳品记录处理中心的数据特性，研究产犊年龄和产犊月份对体细胞评分的影响，并计算种公牛体细胞评分的初步育种值。五个处理中心提供了数据，但在进行中的记录可用性、最后样本日的泌乳天数以及数据提交的时长方面存在显著差异。体细胞评分的最高泌乳期均值在年轻奶牛的短泌乳期较高，而在年长奶牛的长泌乳期较高。该国不同地区产犊月份对体细胞评分泌乳期均值的影响差异很大，但所有乳品记录处理中心的体细胞评分泌乳期均值均随产犊年龄增加而升高。将标准化的牛奶、脂肪和蛋白质产量作为与体细胞评分的多个性状纳入分析。单个处理中心体细胞评分的遗传力为0.08至0.16，所有处理中心的遗传力为0.10。体细胞评分与产量性状的表型相关为负，但遗传相关为正。在全国范围内选择降低体细胞评分应该是可行的，而且似乎有利于减少乳腺炎感染。然而，由于与具有重要经济意义的产量性状存在拮抗遗传关系，反应可能会很缓慢。
