Manfredi E, Ducrocq V, Foulley J L
Station de Génétique Quantitative et Appliquée, Institut National de la Recherche Agronomique, Jouy-en-Josas, France.
J Dairy Sci. 1991 May;74(5):1715-23. doi: 10.3168/jds.S0022-0302(91)78334-3.
Breeding values and genetic parameters for dystocia were estimated in Normande and Holstein breeds. Dystocia scores were related to an underlying continuous variable via a threshold model. The underlying linear model included the effects of calving season, sex of calf by parity of dam, sire of calf, grandsire of calf, dam within maternal grandsire and herd-year effects. Typical results were found for the environmental effects, with a strong influence of dam parity on dystocia, a strong influence of sex of calf, and a small effect of calving season. Herd-year variances were 32 and 40% of the residual variance in the Normande and Holstein breeds, respectively. Heritabilities for the Normande (Holstein) breed were .08 (.07) for direct effects and .11 (.07) for maternal effects. Correlations between sire and grandsire effects were .51 and .36 for the Normande and Holstein breeds, respectively. The corresponding correlations between direct and maternal effects were .15 and -.09. The results of this study show that a complete model for dystocia including the threshold concept and maternal effects can be applied for routine evaluation of dairy AI bulls. Maternal effects are important, and they should be considered in dystocia analysis, especially if nonrandom mating is present. Selection for reducing dystocia in calf and cow effects are not antagonistic.
在诺曼底牛和荷斯坦牛品种中估计了难产的育种值和遗传参数。难产评分通过阈值模型与潜在的连续变量相关。潜在的线性模型包括产犊季节、犊牛性别（按母牛胎次）、犊牛父亲、犊牛祖父、母系祖父内的母牛以及牛群-年份效应的影响。环境效应呈现出典型结果，母牛胎次对难产有强烈影响，犊牛性别影响显著，产犊季节影响较小。牛群-年份方差分别占诺曼底牛和荷斯坦牛品种剩余方差的32%和40%。诺曼底牛（荷斯坦牛）品种的直接效应遗传力为0.08（0.07），母体效应遗传力为0.11（0.07）。诺曼底牛和荷斯坦牛品种中，父亲和祖父效应之间的相关性分别为0.51和0.36。直接效应和母体效应之间的相应相关性分别为0.15和-0.09。本研究结果表明，一个包括阈值概念和母体效应的完整难产模型可用于奶牛人工授精公牛的常规评估。母体效应很重要，在难产分析中应予以考虑，尤其是在存在非随机交配的情况下。选择降低犊牛和母牛的难产效应并非相互对立。
