Linear reaction norm models for genetic merit prediction of Angus cattle under genotype by environment interaction
Linear reaction norm models for genetic merit prediction of Angus cattle under genotype by environment interaction
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DOI：
10.2527/jas.2011-4333
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发表时间：
2012-07-01
影响因子：
3.3
通讯作者：
Tempelman, R. J.
中科院分区：
文献类型：
--
作者：
Cardoso, F. F.;Tempelman, R. J.
这项工作的目的是评估巴西安格斯牛遗传评价的替代线性反应规范（RN）模型。也就是说，我们研究了基因型与环境变化连续描述符之间的相互作用，以检验基因型通过环境相互作用（GxE）影响断奶后体重增加（PWG）的证据，并比较了国产和进口安格斯母猪的环境敏感性。数据由巴西安格斯改良计划从1974年到2005年收集，包括63,098条记录和95,896只动物的谱系文件。采用贝叶斯推理实现了6个模型，并采用偏差信息准则（DIC）进行了比较。最简单的模型是M-1，这是一种传统的动物模型，与考虑GxE的4种替代RN规格相比，它显示出最大的DIC，因此拟合最差。在M-2中，采用M-1的当代群体后验均值作为环境梯度，实施两步手术，范围从-92.6到+265.5 kg。此外，M-3证明了在1步方法中联合估计所有参数的好处。此外，我们扩展了M-3，以允许使用指数函数（M-4）和最佳拟合（最小DIC）环境分类模型（M-5）规范的剩余异方差。最后，M-6只向M-1添加了异方差残差。所有品种的遗传力在恶劣环境下较低，随生产条件的改善而增加。不同环境水平下，M-1和最佳拟合RN模型M-3（均方差）和M-5（异方差）遗传价值预测的秩相关在0.79和0.81之间，表明GxE在巴西安格斯PWG中具有重要的生物学意义。这些结果表明，采用环境特异性遗传优势预测可以优化选择过程。北美原产进口公牛PWG环境敏感性（0.046 +/- 0.009）显著大于本土品种（0.012 +/- 0.013）。在中上等生产水平上，进口品系后代的PWG高于本土品系。另一方面，在巴西当地选择的安格斯牛对环境变化的抵抗力更强，因此在潜在后代的生产环境不确定时更适合。
The objectives of this work were to assess alternative linear reaction norm (RN) models for genetic evaluation of Angus cattle in Brazil. That is, we investigated the interaction between genotypes and continuous descriptors of the environmental variation to examine evidence of genotype by environment interaction (GxE) in post-weaning BW gain (PWG) and to compare the environmental sensitivity of national and imported Angus sires. Data were collected by the Brazilian Angus Improvement Program from 1974 to 2005 and consisted of 63,098 records and a pedigree file with 95,896 animals. Six models were implemented using Bayesian inference and compared using the Deviance Information Criterion (DIC). The simplest model was M-1, a traditional animal model, which showed the largest DIC and hence the poorest fit when compared with the 4 alternative RN specifications accounting for GxE. In M-2, a 2-step procedure was implemented using the contemporary group posterior means of M-1 as the environmental gradient, ranging from -92.6 to +265.5 kg. Moreover, the benefits of jointly estimating all parameters in a 1-step approach were demonstrated by M-3. Additionally, we extended M-3 to allow for residual heteroskedasticity using an exponential function (M-4) and the best fitting (smallest DIC) environmental classification model (M-5) specification. Finally, M-6 added just heteroskedastic residual variance to M-1. Heritabilities were less at harsh environments and increased with the improvement of production conditions for all RN models. Rank correlations among genetic merit predictions obtained by M-1 and by the best fitting RN models M-3 (homoskedastic) and M-5 (heteroskedastic) at different environmental levels ranged from 0.79 and 0.81, suggesting biological importance of GxE in Brazilian Angus PWG. These results suggest that selection progress could be optimized by adopting environment-specific genetic merit predictions. The PWG environmental sensitivity of imported North American origin bulls (0.046 +/- 0.009) was significantly larger (P < 0.05) than that of local sires (0.012 +/- 0.013). Moreover, PWG of progeny of imported sires exceeded that of native sires in medium and superior production levels. On the other hand, Angus cattle locally selected in Brazil tended to be more robust to environmental changes and hence be more suitable when production environments for potential progeny is uncertain.