对同类相食鸡层的生存有社会影响的遗传参数：生存分析与线性动物模型的结合。
Genetic parameters for social effects on survival in cannibalistic layers: combining survival analysis and a linear animal model.
机构信息
Animal Breeding and Genomics Centre, Wageningen University, Marijkeweg 40, 6709PG Wageningen, The Netherlands.
出版信息
Genet Sel Evol. 2010 Jul 7;42(1):27. doi: 10.1186/1297-9686-42-27.
BACKGROUND
Mortality due to cannibalism in laying hens is a difficult trait to improve genetically, because censoring is high (animals still alive at the end of the testing period) and it may depend on both the individual itself and the behaviour of its group members, so-called associative effects (social interactions). To analyse survival data, survival analysis can be used. However, it is not possible to include associative effects in the current software for survival analysis. A solution could be to combine survival analysis and a linear animal model including associative effects. This paper presents a two-step approach (2STEP), combining survival analysis and a linear animal model including associative effects (LAM).
METHODS
Data of three purebred White Leghorn layer lines from Institut de Sélection Animale B.V., a Hendrix Genetics company, were used in this study. For the statistical analysis, survival data on 16,780 hens kept in four-bird cages with intact beaks were used. Genetic parameters for direct and associative effects on survival time were estimated using 2STEP. Cross validation was used to compare 2STEP with LAM. LAM was applied directly to estimate genetic parameters for social effects on observed survival days.
RESULTS
Using 2STEP, total heritable variance, including both direct and associative genetic effects, expressed as the proportion of phenotypic variance, ranged from 32% to 64%. These results were substantially larger than when using LAM. However, cross validation showed that 2STEP gave approximately the same survival curves and rank correlations as LAM. Furthermore, cross validation showed that selection based on both direct and associative genetic effects, using either 2STEP or LAM, gave the best prediction of survival time.
CONCLUSION
It can be concluded that 2STEP can be used to estimate genetic parameters for direct and associative effects on survival time in laying hens. Using 2STEP increased the heritable variance in survival time. Cross validation showed that social genetic effects contribute to a large difference in survival days between two extreme groups. Genetic selection targeting both direct and associative effects is expected to reduce mortality due to cannibalism in laying hens.
背景
在产蛋母鸡中，由于同类相食导致的死亡率是一个难以通过遗传改良来提高的特征，因为死亡率高（在测试期结束时仍存活的动物），并且可能取决于个体本身及其群体成员的行为，即所谓的关联效应（社会互动）。为了分析生存数据，可以使用生存分析。然而，当前的生存分析软件无法包含关联效应。一种解决方案可能是将生存分析与包括关联效应的线性动物模型相结合。本文提出了一种两步法（2STEP），将生存分析与包括关联效应的线性动物模型（LAM）相结合。
方法
本研究使用了 Institut de Sélection Animale B.V.（一家 Hendrix Genetics 公司）的三个纯种白来航层线的数据。对于统计分析，使用了在四禽笼中饲养的 16780 只喙完好的母鸡的生存数据。使用 2STEP 估计了直接和关联效应对生存时间的遗传参数。使用交叉验证比较了 2STEP 与 LAM。LAM 直接用于估计观察到的生存天数对社会效应的遗传参数。
结果
使用 2STEP，包括直接和关联遗传效应在内的总可遗传方差，以表型方差的比例表示，范围为 32%至 64%。这些结果明显大于使用 LAM 时的结果。然而，交叉验证表明，2STEP 与 LAM 给出了大致相同的生存曲线和秩相关。此外，交叉验证表明，基于直接和关联遗传效应的选择，无论是使用 2STEP 还是 LAM，都可以对生存时间进行最佳预测。
结论
可以得出结论，2STEP 可用于估计产蛋母鸡生存时间的直接和关联遗传效应的遗传参数。使用 2STEP 增加了生存时间的可遗传方差。交叉验证表明，社会遗传效应导致两个极端群体之间的生存天数存在较大差异。针对直接和关联效应的遗传选择有望降低产蛋母鸡因同类相食而导致的死亡率。
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