Teagasc, Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, Ireland.
Department of Science, Waterford Institute of Technology, Cork Road, Co. Waterford, Ireland.
J Anim Sci. 2018 May 4;96(5):1628-1639. doi: 10.1093/jas/sky076.
Linear type traits describing the skeletal, muscular, and functional characteristics of an animal are routinely scored on live animals in both the dairy and beef cattle industries. Previous studies have demonstrated that genetic parameters for certain performance traits may differ between breeds; no study, however, has attempted to determine if differences exist in genetic parameters of linear type traits among breeds or sexes. Therefore, the objective of the present study was to determine if genetic covariance components for linear type traits differed among five contrasting cattle breeds, and to also investigate if these components differed by sex. A total of 18 linear type traits scored on 3,356 Angus (AA), 31,049 Charolais (CH), 3,004 Hereford (HE), 35,159 Limousin (LM), and 8,632 Simmental (SI) were used in the analysis. Data were analyzed using animal linear mixed models which included the fixed effects of sex of the animal (except in the investigation into the presence of sexual dimorphism), age at scoring, parity of the dam, and contemporary group of herd-date of scoring. Differences (P < 0.05) in heritability estimates, between at least two breeds, existed for 13 out of 18 linear type traits. Differences (P < 0.05) also existed between the pairwise within-breed genetic correlations among the linear type traits. Overall, the linear type traits in the continental breeds (i.e., CH, LM, SI) tended to have similar heritability estimates to each other as well as similar genetic correlations among the same pairwise traits, as did the traits in the British breeds (i.e., AA, HE). The correlation between a linear function of breeding values computed conditional on covariance parameters estimated from the CH breed with a linear function of breeding values computed conditional on covariance parameters estimated from the other breeds was estimated. Replacing the genetic covariance components estimated in the CH breed with those of the LM had least effect but the impact was considerable when the genetic covariance components of the AA were used. Genetic correlations between the same linear type traits in the two sexes were all close to unity (≥0.90) suggesting little advantage in considering these as separate traits for males and females. Results for the present study indicate the potential increase in accuracy of estimated breeding value prediction from considering, at least, the British breed traits separate to continental breed traits.
线性体型特征描述了动物的骨骼、肌肉和功能特征，在奶牛和肉牛行业中，通常对活体动物进行评分。以前的研究表明，某些性能特征的遗传参数可能因品种而异；然而，尚无研究试图确定品种间线性体型特征的遗传参数是否存在差异。因此，本研究的目的是确定五个不同牛品种的线性体型特征的遗传协方差成分是否存在差异，并研究这些成分是否因性别而异。共分析了 18 个线性体型特征，这些特征是在 3356 头安格斯牛（AA）、31049 头夏洛莱牛（CH）、3004 头赫里福德牛（HE）、35159 头利木赞牛（LM）和 8632 头西门塔尔牛（SI）上进行评分。使用动物线性混合模型分析数据，该模型包括动物的性别（在研究性别二态性时除外）、评分时的年龄、母畜的产仔数和群体的同期-评分日期的固定效应。在 18 个线性体型特征中，有 13 个特征的遗传估计值在至少两个品种之间存在差异（P<0.05）。在同一品种内，线性体型特征之间的遗传相关性也存在差异（P<0.05）。总体而言，大陆品种（即 CH、LM、SI）的线性体型特征彼此之间的遗传估计值相似，并且同一对特征之间的遗传相关性也相似，英国品种（即 AA、HE）也是如此。估计了根据 CH 品种估计的协方差参数和根据其他品种估计的协方差参数条件下的育种值线性函数之间的相关性。用 LM 品种估计的遗传协方差成分替换 CH 品种估计的遗传协方差成分的影响最小，但当 AA 品种的遗传协方差成分被使用时，影响是相当大的。两种性别中相同线性体型特征之间的遗传相关性都接近 1（≥0.90），这表明将这些特征视为男性和女性的单独特征几乎没有优势。本研究的结果表明，考虑至少将英国品种特征与大陆品种特征分开，可能会提高估计育种值预测的准确性。
