Koch R M, Cundiff L V, Gregory K E
Animal Science Department, University of Nebraska, Lincoln 68583-0908, USA.
J Anim Sci. 1995 Oct;73(10):2951-8. doi: 10.2527/1995.73102951x.
An experiment involving crosses among selection and control lines was conducted to partition direct and maternal additive genetic response to 20 yr of selection for 1) weaning weight (WWL), 2) yearling weight (YWL), and 3) an index of yearling weight and muscle score (IXL). Maternal response was estimated from reciprocal crosses among unselected sires and dams of control (CTL) and the selection lines. An Angus line was added to increase the number of reciprocal cross comparisons. Direct responses of WWL, YWL, and IXL linebreds compared with CTL were significant for all traits. Maternal genetic responses were much smaller than direct responses. Direct response in birth weight was largest for YWL, followed by WWL and IXL. Maternal effect of IXL on birth weight was larger and that of WWL and YWL was smaller than CTL. Direct responses in weaning weight did not differ greatly among selection lines; maternal response was greater for IXL than for WWL, which was selected for this trait, and response was negative for YWL. Responses in maternal effects on final weight were much reduced in Hereford crosses because of a negative relation between maternal responses in pre- and postweaning gains, especially in YWL and IXL. However, in Angus crosses, a positive association between pre- and postweaning gains increased maternal responses in final weight. Direct response for postweaning gain was greater in IXL than in YWL of WWL in Hereford crosses. In Angus crosses, YWL had larger direct responses for birth weight, preweaning gain, and postweaning gain than in other lines. The direct response for muscle score from selection in IXL, which was selected for muscle score and yearling weight, was greater than in other lines; maternal response was not important. The greatest gain in final weight was obtained when selection resulted in a favorable change in the total of direct and maternal effects pre- and postweaning, which in this experiment was provided by including a muscle score along with yearling weight as selection criteria.
开展了一项涉及选择系与对照系杂交的实验，以区分对20年选择的直接加性遗传效应和母体加性遗传效应，选择的性状为：1) 断奶体重（WWL），2) 周岁体重（YWL），以及3) 周岁体重与肌肉评分指数（IXL）。母体效应通过对照系（CTL）和选择系未选择的公母畜之间的正反交来估计。添加了一个安格斯系以增加正反交比较的数量。与CTL相比，WWL、YWL和IXL品系纯合子在所有性状上的直接反应均显著。母体遗传效应远小于直接效应。周岁体重在出生体重上的直接反应最大，其次是断奶体重和周岁体重与肌肉评分指数。周岁体重与肌肉评分指数对出生体重的母体效应大于CTL，而断奶体重和周岁体重的母体效应小于CTL。各选择系在断奶体重上的直接反应差异不大；周岁体重与肌肉评分指数的母体反应大于断奶体重（该性状的选择对象），周岁体重的反应为负。在海福特牛杂交中，由于断奶前和断奶后增重的母体反应呈负相关，尤其是在周岁体重和周岁体重与肌肉评分指数中，母体对最终体重的效应反应大幅降低。然而，在安格斯牛杂交中，断奶前和断奶后增重之间的正相关增加了母体对最终体重的反应。在海福特牛杂交中，周岁体重与肌肉评分指数断奶后增重的直接反应大于断奶体重的周岁体重。在安格斯牛杂交中，周岁体重在出生体重、断奶前增重和断奶后增重方面的直接反应大于其他品系。在同时选择肌肉评分和周岁体重的周岁体重与肌肉评分指数中，选择对肌肉评分的直接反应大于其他品系；母体反应并不重要。当选择导致断奶前和断奶后直接效应与母体效应的总和产生有利变化时，最终体重获得了最大增益，在本实验中，这是通过将肌肉评分与周岁体重一起作为选择标准来实现的。
