A multivariate model was developed and used to estimate genetic parameters of body weight (BW) at 1-6 weeks of age of broilers raised in a commercial environment. The development of model was based on the predictive ability of breeding values evaluated from a cross-validation procedure that relied on half-sib correlation. The multivariate model accounted for heterogeneous variances between sexes through standardization applied to male and female BWs differently. It was found that the direct additive genetic, permanent environmental maternal and residual variances for BW increased drastically as broilers aged. The drastic increase in variances over weeks of age was mainly due to scaling effects. The ratio of the permanent environmental maternal variance to phenotypic variance decreased gradually with increasing age. Heritability of BW traits ranged from 0.28 to 0.33 at different weeks of age. The direct genetic effects on consecutive weekly BWs had high genetic correlations (0.85-0.99), but the genetic correlations between early and late BWs were low (0.32-0.57). The difference in variance components between sexes increased with increasing age. In conclusion, the permanent environmental maternal effect on broiler chicken BW decreased with increasing age from weeks 1 to 6. Potential bias of the model that considered identical variances for sexes could be reduced when heterogeneous variances between sexes are accounted for in the model.

中文翻译：

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商品化环境饲养肉鸡不同龄期体重的遗传分析

开发了一个多变量模型并用于估计在商业环境中饲养的肉鸡 1-6 周龄体重 (BW) 的遗传参数。模型的开发基于从依赖于半同胞相关性的交叉验证程序评估的育种值的预测能力。多变量模型通过不同地应用于男性和女性 BW 的标准化来解释性别之间的异质差异。结果表明，随着肉鸡年龄的增长，BW 的直接加性遗传、永久环境母体和残余变异急剧增加。周龄差异的急剧增加主要是由于缩放效应。永久性环境母体变异与表型变异的比值随着年龄的增加而逐渐降低。BW 性状的遗传力在不同周龄范围从 0.28 到 0.33。对连续每周 BW 的直接遗传效应具有较高的遗传相关性（0.85-0.99），但早期和晚期 BW 之间的遗传相关性较低（0.32-0.57）。两性之间方差分量的差异随着年龄的增加而增加。总之，环境母体对肉鸡体重的永久性影响随着年龄从第 1 周到第 6 周的增加而降低。当模型中考虑了性别之间的异质方差时，可以减少考虑性别相同方差的模型的潜在偏差。两性之间方差分量的差异随着年龄的增加而增加。总之，环境母体对肉鸡体重的永久性影响随着年龄从第 1 周到第 6 周的增加而降低。当模型中考虑了性别之间的异质方差时，可以减少考虑性别相同方差的模型的潜在偏差。两性之间方差分量的差异随着年龄的增加而增加。总之，环境母体对肉鸡体重的永久性影响随着年龄从第 1 周到第 6 周的增加而降低。当模型中考虑了性别之间的异质方差时，可以减少考虑性别相同方差的模型的潜在偏差。