Balcerzak K M, Freeman A E, Willham R L
Iowa State University, Ames 50011.
J Dairy Sci. 1989 May;72(5):1273-9. doi: 10.3168/jds.S0022-0302(89)79232-8.
The effects of selection for the direct and maternal components of dystocia were estimated for first, second and later, and all parities. The effect of restricting maternal change to zero and the effect of selection for only the direct component were also examined. Gene flow procedure was used to compute economic weights as 1 and .347 for the direct and maternal effects, respectively. Genetic gain in aggregate genotype was the largest for first parity. For all parities all the gain in the aggregate genotype was accounted for by the direct effects. At the same time, a slight decrease in the genetic maternal effects was observed. For all cases, selection for both traits had almost no loss in aggregate genotype or accuracy compared with when maternal changes were restricted to zero. Total genetic gain and genetic gain for the direct effect of dystocia were greater and accuracy of selection was lower when selection was for the genetic direct effect only versus the index that included both direct and maternal effects. Selection for only the direct effects is not likely to produce any significant change in dystocia as a maternal trait.
针对初产、经产和多胎产母猪难产的直接效应和母体效应选择效果进行了评估。同时还研究了将母体效应变化限制为零的效果以及仅针对直接效应进行选择的效果。采用基因流动程序分别计算直接效应和母体效应的经济权重为1和0.347。初产母猪总基因型的遗传进展最大。对于所有胎次，总基因型的所有进展均由直接效应导致。同时，观察到母体遗传效应略有下降。对于所有情况，与将母体效应变化限制为零时相比，同时选择这两个性状在总基因型或准确性方面几乎没有损失。与同时包含直接效应和母体效应的指数相比，仅针对难产的遗传直接效应进行选择时，总遗传进展和直接效应的遗传进展更大，但选择准确性较低。仅针对直接效应进行选择不太可能使难产作为母体性状产生任何显著变化。
