Animal and Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Co., Cork, Ireland.
Irish Cattle Breeding Federation, Highfield House, Bandon, Co., Cork, Ireland.
J Anim Sci. 2020 Nov 1;98(11). doi: 10.1093/jas/skaa322.
Despite the importance of validating any technology prior to recommendation for use, few studies exist in the scientific literature which have demonstrated the superior performance of high-ranking animals in a given total merit index; this is especially true for maternal cattle selection indexes. The objective of the present study was to demonstrate the impact of the Irish total merit maternal-based index and provide the benefits of using the Irish total merit maternal-based beef index as part of a breeding policy. The validation exercise was undertaken using 269,407 records (which included the cow's own records and her progeny records) from 92,300 females differing in a total merit index for maternal value; a comparison was also made with the Irish terminal index. Association analyses were undertaken within the framework of linear and threshold mixed models; the traits analyzed were fertility (e.g., calving interval), slaughter (e.g., harvest weight), live weight (e.g., weaning weight), and producer-recorded traits (e.g., docility). All traits were analyzed with the maternal index and terminal index fitted as covariate(s) separately. Depending on the independent variable analyzed, the other fixed effects included: parity of cow, heterosis and recombination loss of cow and/or progeny, gender of progeny, and the estimated breeding value of the sire; contemporary group was included as a random effect. The results demonstrate the effectiveness of using total merit indexes to improve performance in a whole range of different traits, despite the often antagonistic genetic correlations among traits that underpin the index. Cows excelling on the maternal index had less calving difficulty, superior fertility performance, lighter carcasses, and live weight, as well as being more easily managed. Additionally, progeny of higher maternal index cows were lighter at birth and more docile albeit with a small impact on slaughter traits. In contrast, higher terminal index cows had more calving difficulty, compromised fertility and had heavier carcasses themselves as well as their progeny. While the differences in phenotypic performance between groups on maternal index was, in most instances, relatively small, the benefits are: (1) expected to be greater when more genetically extreme groups of animals are evaluated and (2) expected to accumulate over time given the cumulative and permanent properties of breeding schemes.
尽管在推荐使用任何技术之前验证其有效性非常重要，但在科学文献中很少有研究表明在给定的总绩效指数中排名较高的动物具有卓越的性能；这在母畜选择指数中尤其如此。本研究的目的是展示爱尔兰基于总绩效的母系指数的影响，并提供使用爱尔兰基于总绩效的母系牛肉指数作为育种政策一部分的好处。验证工作使用了 92,300 头母牛的 269,407 条记录（包括母牛自身的记录及其后代的记录），这些母牛在母系价值的总绩效指数方面存在差异；还与爱尔兰终端指数进行了比较。关联分析是在线性和阈值混合模型的框架内进行的；分析的特征包括繁殖力（例如，产犊间隔）、屠宰（例如，收获体重）、活体重（例如，断奶体重）和生产者记录的特征（例如，温顺性）。所有特征均与母系指数和终端指数作为协变量进行分析。根据分析的自变量，其他固定效应包括：母牛的胎次、杂种优势和母牛及/或后代的重组损失、后代的性别以及公牛的估计育种值；将当代群体作为随机效应包含在内。结果表明，尽管构成指数的特征之间存在遗传相关性，但使用总绩效指数可以有效地提高一系列不同特征的表现。在母系指数上表现出色的母牛分娩困难较小、繁殖性能较好、胴体较轻、活体重较高，并且更容易管理。此外，母系指数较高的母牛的后代出生时体重较轻，且更加温顺，尽管对屠宰特征的影响较小。相反，终端指数较高的母牛分娩困难更大，繁殖力受损，自身及其后代的胴体较重。虽然群体之间在母系指数上的表型表现差异在大多数情况下相对较小，但好处是：(1) 在评估遗传上更为极端的动物群体时预计会更大，以及 (2) 鉴于育种计划的累积和永久性，随着时间的推移会不断积累。
