Abstract：
In beef cattle, dams play a crucial role in shaping the pre- and postnatal environment for the growth of their offspring. Acknowledging the substantial impact of maternal influence on the early development of calves, researchers utilize maternal animal models. These models take into account both maternal genetic and permanent environmental effects, operating under the assumption that these influences remain constant throughout the productive life of the cow. Nevertheless, it cannot be ruled out that these genetic and environmental effects may evolve throughout the lifespan of the cows. Therefore, this study aims to describe the changes in genetic and environmental maternal effects over the productive lifespan of cows. To accomplish this goal, we utilized random regression models, incorporating the age of the dam effect, maternal genetic effects, and environmental permanent effects using Legendre orthogonal polynomials. Additionally, the analytical model incorporated a covariate to adjust for the calf\'s age at recording, a two-level sex effect, a random herd-year-season effect, and an additive direct genetic effect associated linked to the calf. The dataset comprised information from dams aged between 2 and 16 years, resulting in a final database that comprised weight records of 58 332 calves from 21 673 dams. The average weight at 90 days was 135.0 ± 39.3 kg, and the mean age of the dam at calving was 7.03 ± 3.41 years. We evaluated models incorporating 2, 3, 4, 5, and 6 orthogonal polynomials alongside the standard maternal animal model. Afterward, we selected the model with five orthogonal polynomials based on the Akaike Information Criteria. The Restricted Maximum Likelihood estimates within this model indicated a direct heritability of around 0.50, and a maternal heritability ranging between 0.15 and 0.25, exhibiting a consistent increase between 4, 5 to 13 years. The genetic correlation estimates between direct and maternal genetic effects remained stable at approximately -0.55 across the lifespan of the cows. Furthermore, maternal genetic correlations between different ages of the dam decreased to around 0.7 for more distant age points. The maternal permanent correlations were notably lower, occasionally even reaching negative values, suggesting variability in environmental influence on maternal effects over the productive lifespan of the cow. Finally, the model enables the prediction of breeding values for the maternal genetic effects of the cow across its lifespan, providing opportunities for innovative selection strategies on the maternal side.
摘要：
在肉牛中，水坝在塑造后代生长的产前和产后环境中起着至关重要的作用。承认母性影响对小牛早期发育的重大影响，研究人员利用母体动物模型。这些模型考虑了母体遗传和永久性环境影响，假设这些影响在奶牛的整个生产寿命中保持不变。然而，不能排除这些遗传和环境影响可能在奶牛的整个生命周期中演变。因此,这项研究旨在描述母牛生产寿命中遗传和环境对母牛影响的变化。为了实现这个目标,我们利用随机回归模型，结合大坝效应的年龄，母体遗传效应，和使用勒让德正交多项式的环境永久效应。此外,分析模型包含了一个协变量来调整小腿在记录时的年龄，两级性效应,随机的羊群年季效应，和与小牛相关的附加直接遗传效应。该数据集包括来自2至16岁的大坝的信息，最终数据库包含21.673水坝中58.332只小牛的体重记录。90天的平均体重为135.0±39.3公斤，大坝的平均年龄为7.03±3.41岁。我们评估了包含2、3、4、5和6个正交多项式以及标准母体动物模型的模型。之后,我们根据Akaike信息准则选择了具有五个正交多项式的模型。该模型中的限制最大似然估计表明，直接遗传力约为0.50，母体遗传力在0.15至0.25之间，在4、5至13年之间表现出持续增加。在奶牛的整个寿命中，直接遗传效应和母体遗传效应之间的遗传相关性估计保持稳定在约-0.55。此外，对于更远的年龄点，大坝不同年龄之间的母体遗传相关性降低到0.7左右。母亲的永久性相关性明显较低，偶尔甚至达到负值，表明环境影响对母牛生产寿命的影响的变异性。最后,该模型能够预测母牛在其寿命内的母体遗传效应的育种值，为母亲方面的创新选择策略提供机会。
