Department of Animal and Dairy Science, University of Georgia, Athens, GA 30602, USA.
Cobb-Vantress, Inc., Siloam Springs, AR 72761, USA.
J Anim Sci. 2024 Jan 3;102. doi: 10.1093/jas/skae190.
Mortality is an economically important trait usually handled as a discrete outcome from hatch time until selection in most broiler breeder programs. However, in other species, it has been shown that not only does the genetic component change over time, but also there are maternal genetic effects to be considered when mortality is recorded early in life. This study aimed to investigate alternative trait definitions of mortality with varying models and effects. Three years' worth of data were provided by Cobb-Vantress, Inc. and included 2 mortality traits. The first trait was binary, whether the bird died or not (OM), and the second trait was a categorical weekly mortality trait. After data cleaning, 6 wk of data for the 2 given mortality traits were used to develop 5 additional trait definitions. The definitions were broiler mortality (BM), early and late mortality (EM & LM), and 2 traits with repeated records as cumulative or binary (CM and RM, respectively). Variance components were estimated using linear and threshold models to investigate whether either model had a benefit. Genomic breeding values were predicted using the BLUP90 software suite, and linear regression validation (LR) was used to compare trait definitions and models. Heritability estimates ranged from 0.01 (0.00) to 0.16 (0.01) under linear and 0.04 (0.01) to 0.21 (0.01) under threshold models, indicating genetic variability within the population across these trait definitions. The genetic correlation between EM and LM ranged from 0.48 to 0.81 across the different lines, indicating they have divergent genetic backgrounds and should be considered different traits. The LR accuracies showed that EM and LM used together in a 2-trait model have comparable accuracies to that of OM while giving a more precise picture of mortality. When including the maternal effect, the direct heritability considerably decreased for EM, indicating that the maternal effect plays an important role in early mortality. Therefore, a suitable approach would be a model with EM and LM while considering the maternal effect for EM. Single nucleotide polymorphism effects were estimated, and no individual SNP explained more than 1% of the additive genetic variance. Additionally, the SNP with the largest effect size and variance were inconsistent across trait definitions. Chicken mortality can be defined in different ways, and reviewing these definitions and models may benefit poultry breeding programs.
死亡率是一个重要的经济性状，在大多数肉鸡育种计划中，通常从孵化时间到选择结束作为一个离散的结果进行处理。然而，在其他物种中，已经表明不仅遗传组成随时间而变化，而且在生命早期记录死亡率时，还需要考虑母体遗传效应。本研究旨在探讨不同模型和效应下死亡率的替代性状定义。Cobb-Vantress, Inc. 提供了三年的数据，包括两个死亡率性状。第一个性状是二元的，即鸟类是否死亡（OM），第二个性状是每周死亡率的分类性状。在数据清理后，使用 2 个给定死亡率性状的 6 周数据开发了另外 5 个性状定义。这些定义是肉鸡死亡率（BM）、早期和晚期死亡率（EM 和 LM），以及具有重复记录的两个性状，分别为累积或二元（CM 和 RM）。使用线性和阈值模型估计方差分量，以研究是否任何模型都有优势。使用 BLUP90 软件套件预测基因组育种值，并使用线性回归验证（LR）比较性状定义和模型。在线性模型下，遗传力估计值范围为 0.01（0.00）至 0.16（0.01），在阈值模型下，遗传力估计值范围为 0.04（0.01）至 0.21（0.01），表明这些性状定义下群体内存在遗传变异性。不同系间 EM 和 LM 之间的遗传相关性在 0.48 到 0.81 之间，表明它们具有不同的遗传背景，应该被视为不同的性状。LR 准确性表明，在 2 个性状模型中同时使用 EM 和 LM 的准确性与 OM 相当，但能更准确地描述死亡率。当包括母体效应时，EM 的直接遗传力显著降低，表明母体效应在早期死亡率中起着重要作用。因此，一种合适的方法是在考虑 EM 的母体效应的同时，使用 EM 和 LM 的模型。估计了单核苷酸多态性效应，没有单个 SNP 解释超过 1%的加性遗传方差。此外，不同性状定义的 SNP 效应大小和方差不一致。鸡死亡率可以用不同的方式定义，审查这些定义和模型可能会使家禽育种计划受益。
