Center for Quantitative Genetics and Genomics, Department of Molecular Biology and Genetics, Aarhus University, 8830, Tjele, Denmark.
SEGES, Pig Research Centre, 1609, Copenhagen, Denmark.
Genet Sel Evol. 2018 Aug 14;50(1):42. doi: 10.1186/s12711-018-0413-y.
Records on groups of individuals rather than on single individuals could be valuable for predicting breeding values (BV) of the traits that are difficult or costly to measure individually, such as feed intake in pigs or beef cattle. Here, we present a model, which handles group records from varying group sizes and involves multiple fixed and random effects, for estimating variance components and predicting BV. Moreover, using simulation, we investigated the efficiency of group records for predicting BV in situations with various group sizes and structures, and factors that affect the trait.
The results show that the presented model for group records worked well and that variances estimated from group records with varying group sizes were consistent with those estimated from individual records, but with larger standard errors. Ignoring litter and pen effects had very little or no influence on the accuracy of estimated BV (EBV) obtained from group records. However, ignoring litter effects resulted in biased estimates of additive genetic variance and EBV. The presence of litter and pen effects on phenotypes decreased the accuracy of EBV although the prediction model fitted both effects. Having more littermates in the same pen led to a higher accuracy of EBV. The decay of EBV accuracy with increasing group size was more marked for scenarios with litter and pen effects than without. When litters of six individuals were divided into two pens, accuracies of EBV obtained from group records with a size up to 12 (average 9.6) and up to 24 (average 19.2) were 66.6 and 57.6% of those estimated from individual records in the scenario with litter and pen effects on phenotypes. These percentages reached 77.0 and 68.4% in the scenario without litter and pen effects on phenotypes.
Our results indicate that the model works appropriately for the analysis of group records from varying group sizes. Using group records for genetic evaluation of traits such as feed intake in pig is feasible and the efficiency of the resulting estimates depends on the size and structure of the groups and on the magnitude of the variances for litter and pen effects.
对于那些难以或难以单独测量的性状（如猪或肉牛的采食量），记录个体群体而非个体的记录可能对预测育种值（BV）很有价值。在这里，我们提出了一种模型，用于处理不同群体大小的群体记录，并涉及多个固定和随机效应，以估计方差分量并预测 BV。此外，通过模拟，我们研究了在具有不同群体大小和结构以及影响性状的因素的情况下，使用群体记录预测 BV 的效率。
结果表明，所提出的群体记录模型运行良好，并且从具有不同群体大小的群体记录中估计的方差与从个体记录中估计的方差一致，但标准误差较大。忽略窝和栏效应对从群体记录中获得的估计 BV（EBV）的准确性几乎没有影响或没有影响。然而，忽略窝效应会导致加性遗传方差和 EBV 的估计值偏置。尽管预测模型拟合了这两个效应，但窝和栏效应对表型的存在降低了 EBV 的准确性。在同一栏中具有更多的同窝仔导致 EBV 的准确性更高。随着群体大小的增加，EBV 准确性的衰减在具有窝和栏效应的情况下比没有窝和栏效应的情况下更为明显。当六头个体的窝被分成两个栏时，在具有窝和栏效应的情况下，从群体记录中获得的大小高达 12（平均 9.6）和高达 24（平均 19.2）的 EBV 的准确性分别为个体记录中 EBV 估计值的 66.6%和 57.6%。在没有窝和栏效应的情况下，这些百分比分别达到 77.0%和 68.4%。
我们的结果表明，该模型适用于分析不同群体大小的群体记录。使用群体记录对猪的采食量等性状进行遗传评估是可行的，并且所得估计值的效率取决于群体的大小和结构以及窝和栏效应的方差大小。
