Kennedy B W, Trus D
Centre for Genetic Improvement of Livestock, University of Guelph, Ontario, Canada.
J Anim Sci. 1993 Sep;71(9):2341-52. doi: 10.2527/1993.7192341x.
Connectedness among management units (e.g., herds or regions) is of concern in genetic evaluation. When genetic evaluation is under an animal model, connections occur through A, the numerator relationship matrix. It is argued that the most appropriate measure of connectedness is the average prediction error variance (PEV) of differences in EBV between animals in different management units. It is shown that PEV of differences is influenced by average genetic relationship between and within management units, which in turn affects the variances of estimates of differences between management unit effects. When PEV of differences cannot be computed, use of one of three alternative measures is proposed; the gene-flow method that measures the exchange of genes between management units, measurement of genetic drift variance based on average relationships between and within management units, and measurement of the variance of estimated differences between management units effects. These were correlated with PEV of differences in a test simulation. The gene-flow method, which is simplest to compute, had the lowest correlation (.671). The drift variance and variance of management unit effects methods were highly correlated with PEV of differences (.924 and .995, respectively).
在遗传评估中，管理单元（如畜群或地区）之间的连通性备受关注。当遗传评估采用动物模型时，连通性通过分子亲缘关系矩阵A体现。有人认为，连通性的最合适度量是不同管理单元中动物之间估计育种值（EBV）差异的平均预测误差方差（PEV）。研究表明，差异的PEV受管理单元之间及内部的平均遗传关系影响，而这又会影响管理单元效应差异估计值的方差。当无法计算差异的PEV时，建议使用三种替代度量之一：测量管理单元之间基因交换的基因流方法、基于管理单元之间及内部平均关系测量遗传漂变方差，以及测量管理单元效应估计差异的方差。在一个测试模拟中，这些与差异的PEV相关。计算最简单的基因流方法，相关性最低（0.671）。漂变方差和管理单元效应方法与差异的PEV高度相关（分别为0.924和0.995）。
