安格斯牛18月龄体尺体重性状遗传参数分析

为分析不同动物模型对宁夏地区安格斯牛18月龄生长性状遗传参数估计的影响，筛选出估计生长性状遗传参数的最佳动物模型，本研究使用包含或剔除母体遗传效应、母体永久环境效应及母体与直接遗传效应之间是否存在协方差来区分６种动物模型，借助DMU软件的DMU_AI模块，利用约束最大似然法（AI-REML）估计安格斯牛18月龄生长性状的遗传参数。利用赤池信息准则（AIC）和似然比检验（LRT）确定遗传参数估计的最佳动物模型。结果表明：1）模型４是估计安格斯牛18月龄体重（Body weight， BW）、十字部高（Crucifixion height， CH）和管围（Shin circumference， SC）的最佳模型，该模型估计的以上3个性状的直接遗传力分别为0.42、0.29和0.22，母体遗传力分别为0.11、0.14和0.05，总遗传力分别为0.23、0.12和0.11。 2）模型6是估计安格斯牛18月龄体高（Body height， BH）、体斜长（Body length， BL）和胸围（Chest circumference， CC）的最佳模型，该模型估计的这些性状的直接遗传力分别为0.48、0.48和0.64，母体遗传力分别为0.02、0.12和0.08，总遗传力分别0.33、0.18和0.34。综上，考虑直接遗传效应和母体遗传效应之间的协方差、母体效应可对目的性状更加准确的进行无偏预测。本研究为加快安格斯牛的遗传进展提供理论依据。

Analysis of genetic parameters for body size and weight traits in Angus cattle at 18 months of age

The study was to analyze the effects of different animal models on the estimation of genetic parameters of growth traits in Angus cattle at 18 months of age in Ningxia， and to screen out the best animal models for estimating genetic parameters of growth traits. In this study， six animal models were distinguished using the inclusion or exclusion of maternal genetic effects， maternal permanent environmental effects and the presence or absence of covariance between maternal and direct genetic effects， and the genetic parameters of 18-month-old growth traits in Angus cattle were estimated using the constrained maximum likelihood method （AI-REML） with the help of the DMU_AI module of DMU software. The best animal model for genetic parameter estimation was determined using the Akaike Information Criterion （AIC） and Likelihood Ratio Test （LRT）. The results showed that： 1） Model 4 was the best model for estimating body weight （BW）， crucifixion height （CH） and shin circumference （SC） in Angus cows at 18 months of age， and the direct heritability of the above three traits estimated by this model was 0.42， 0.29 and 0.22， respectively. Maternal heritability was 0.11， 0.14 and 0.05， respectively， and total heritability was 0.23， 0.12 and 0.11， respectively. 2） Model 6 was the best model for estimating body height （BH）， body length （BL） and chest circumference （CC） in 18-month-old Angus cows， and the estimated direct heritability for these traits was 0.42， 0.29 and 0.22， respectively， and the estimated direct heritability for the above three traits was 0.11， 0.14 and 0.05， respectively. The estimated direct heritability of these traits was 0.48， 0.48 and 0.64， the maternal heritability was 0.02， 0.12 and 0.08， and the total heritability was 0.33， 0.18 and 0.34， respectively. In summary， considering the covariance and maternal effects between direct genetic effects and maternal genetic effects， and maternal effects allows for more accurate and unbiased prediction of the target trait. This study provides a theoretical basis for accelerating genetic progress in Angus cattle.