MacNeil M D, Cardoso F F, Hay E
J Anim Sci. 2017 Sep;95(9):3833-3838. doi: 10.2527/jas2017.1829.
It has long been recognized that genotype × environment interaction potentially influences genetic evaluation of beef cattle. However, this recognition has largely been ignored in systems for national cattle evaluation. The objective of this investigation was to determine if direct and maternal genetic effects on preweaning gain would be reranked depending on an environmental gradient as determined by year effects. Data used were from the 76-yr selection experiment with the Line 1 Hereford cattle raised at Miles City, MT. The data comprised recorded phenotypes from 7,566 animals and an additional 1,862 ancestral records included in the pedigree. The presence of genotype × environment interaction was examined using reaction norms wherein year effects on preweaning gain were hypothesized to linearly influence the EBV. Estimates of heritability for direct and maternal effects, given the average environment, were 10 ± 2 and 26 ± 3%, respectively. In an environment that is characterized by the 5th (95th) percentile of the distribution of year effects, the corresponding estimates of heritability were 18 ± 3 (22 ± 3%) and 30 ± 3% (30 ± 3%), respectively. Rank correlations of direct and maternal EBV appropriate to the 5th and 95th percentiles of the year effects were 0.67 and 0.92, respectively. In the average environment, the genetic trends were 255 ± 1 g/yr for direct effects and 557 ± 3 g/yr for maternal effects. In the fifth percentile environment, the corresponding estimates of genetic trend were 271 ± 1 and 540 ± 3 g/yr, respectively, and in the 95th percentile environment, they were 236 ± 1 and 578 ± 3 g/yr, respectively. Linear genetic trends in environmental sensitivity were observed for both the direct (-8.06 × 10 ± 0.49 × 10) and maternal (8.72 × 10 ± 0.43 × 10) effects. Therefore, changing systems of national cattle evaluation to more fully account for potential genotype × environment interaction would improve the assessment of breeding stock, particularly for direct effects. Estimates of environmental sensitivity parameters could also facilitate identification of genetic limitations to production.
长期以来，人们已经认识到基因型×环境互作可能会影响肉牛的遗传评估。然而，这种认识在国家牛群评估系统中基本上被忽视了。本研究的目的是确定断奶前增重的直接遗传效应和母体遗传效应是否会根据年份效应所确定的环境梯度而重新排序。所使用的数据来自于在蒙大拿州迈尔斯城饲养的1系赫里福德牛的76年选择试验。数据包括7566头动物的记录表型以及系谱中另外1862条祖先记录。使用反应规范来检验基因型×环境互作的存在，其中假设年份对断奶前增重的影响会线性影响估计育种值（EBV）。在平均环境下，直接效应和母体效应的遗传力估计值分别为10±2%和26±3%。在以年份效应分布的第5（95）百分位数为特征的环境中，相应的遗传力估计值分别为18±3%（22±3%）和30±3%（30±3%）。对应于年份效应第5和95百分位数的直接EBV和母体EBV的秩相关分别为0.67和0.92。在平均环境下，直接效应的遗传趋势为255±1克/年，母体效应的遗传趋势为557±3克/年。在第5百分位数环境中，相应的遗传趋势估计值分别为271±1克/年和540±3克/年，在第95百分位数环境中，分别为236±1克/年和578±3克/年。在直接效应（-8.06×10±0.49×10）和母体效应（8.72×10±0.43×10）中均观察到了环境敏感性的线性遗传趋势。因此，改变国家牛群评估系统以更全面地考虑潜在的基因型×环境互作将改善种畜的评估，特别是对于直接效应。环境敏感性参数的估计也有助于识别生产的遗传限制因素。
