School of Environmental and Rural Science, University of New England, Armidale, NSW, 2351, Australia.
Animal Genetics and Breeding Unit, University of New England, Armidale, NSW, 2351, Australia.
Genet Sel Evol. 2024 Aug 6;56(1):57. doi: 10.1186/s12711-024-00924-4.
The effects of environmental disturbances on livestock are often observed indirectly through the variability patterns of repeated performance records over time. Sheep are frequently exposed to diverse extensive environments but currently lack appropriate measures of resilience (or sensitivity) towards environmental disturbance. In this study, random regression models were used to analyse repeated records of the fibre diameter of wool taken along the wool staple (bundle of wool fibres) to investigate how the genetic and environmental variance of fibre diameter changes with different growing environments.
A model containing a fifth, fourth and second-order Legendre polynomial applied to the fixed, additive and permanent environmental effects, respectively, was optimal for modelling fibre diameter along the wool staple. The additive genetic and permanent environmental variance both showed variability across the staple length trajectory. The ranking of sire estimated breeding values (EBV) for fibre diameter was shown to change along the staple and the genetic correlations decreased as the distance between measurements along the staple increased. This result suggests that some genotypes were potentially more resilient towards the changes in the growing environment compared to others. In addition, the eigenfunctions of the random regression model implied the ability to change the fibre diameter trajectory to reduce its variability along the wool staple.
These results show that genetic variation in fibre diameter measured along the wool staple exists and this could be used to provide greater insight into the ability to select for resilience in extensively raised sheep populations.
环境干扰对家畜的影响通常通过随时间推移的重复性能记录的可变性模式间接观察到。绵羊经常暴露在多样化的广泛环境中，但目前缺乏对环境干扰的恢复力（或敏感性）的适当衡量标准。在这项研究中，使用随机回归模型分析了羊毛纤维直径的重复记录，这些记录是沿着羊毛毛束（一束羊毛纤维）取得的，以研究纤维直径的遗传和环境方差如何随不同的生长环境而变化。
一个包含第五、第四和二阶勒让德多项式的模型，分别应用于固定、加性和永久环境效应，是对毛束上纤维直径进行建模的最佳模型。加性遗传和永久环境方差都在毛束长度轨迹上表现出可变性。纤维直径的 sire 估计育种值（EBV）的排名随着毛束的长度而变化，并且随着沿着毛束的测量距离增加，遗传相关性降低。这一结果表明，与其他基因型相比，某些基因型可能对生长环境的变化更具恢复力。此外，随机回归模型的本征函数暗示了改变纤维直径轨迹以降低其沿着毛束的可变性的能力。
这些结果表明，沿着羊毛毛束测量的纤维直径存在遗传变异，这可以提供更多关于选择对广泛饲养的绵羊群体的恢复力的洞察力。
