Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Växa, Uppsala, Sweden.
J Anim Breed Genet. 2023 Jul;140(4):366-375. doi: 10.1111/jbg.12764. Epub 2023 Feb 27.
Assessment protocols to describe the various aspects of conformation, gait and jumping traits on a linear scale were introduced at young horse tests for Swedish Warmblood horses in 2013. The traits scored on a linear scale are assumed to be less subjective and more easily compared across populations than the traditional evaluated traits that are scored relative to the breeding goal. However, the resulting number of traits is considerable, and several of the traits are correlated. The aim of this study was to investigate the interrelationship between the different evaluated and linearly scored traits in Swedish Warmbloods using factor analysis. In total, 20,935 horses born 1996-2017 had information on evaluated traits, and 5450 of these also had linearly scored trait records assessed since 2014 when the protocol was updated. A factor analysis with varimax rotation was performed separately for evaluated and linearly scored traits using the Psych package in R. Height at withers was included in both analyses. A total of four factors for evaluated traits and 14 factors for linearly scored traits were kept for further analysis. Missing values for individual traits in horses with linearly scored trait records were imputed based on correlated traits before factor scores were calculated using factor loadings. Genetic parameters for, and correlations between, the resulting underlying factors were estimated using multiple-trait animal models in the BLUPF90 package. Heritability estimates were on a similar level as for the traits currently used in the genetic evaluation, ranging from 0.05 for the factor for linearly scored traits named L.behaviour (dominated by traits related to behaviour) to 0.59 for the factor for evaluated traits named E.size (dominated by height at withers and conformation). For both types of traits, separate factors were formed for jumping and gait traits, as well as for body size. High genetic correlations were estimated between such corresponding factors for evaluated traits and factors for linearly scored traits. In conclusion, factor analysis could be used to reduce the number of traits to be included in multiple-trait genetic evaluation or in genomic analysis for warmblood horses. It can also contribute to a better understanding of the interrelationships among the assessed traits and be useful to decide on subgroups of traits to be used in several multiple-trait evaluations on groups of original traits.
2013 年，瑞典温血马青年马测试引入了评估方案，以线性尺度描述 conformation（ conformation ）、步态和跳跃性状的各个方面。与传统的相对于育种目标进行评分的评估性状相比，线性尺度上评分的性状被认为主观性更小，更容易在不同群体之间进行比较。然而，产生的性状数量相当多，并且其中一些性状是相关的。本研究旨在使用因子分析研究瑞典温血马中不同评估和线性评分性状之间的相互关系。共有 20935 匹 1996-2017 年出生的马有评估性状的信息，其中 5450 匹马自 2014 年评估方案更新以来也有线性评分性状记录。使用 R 中的 Psych 包分别对评估和线性评分性状进行因子分析和最大方差旋转。在这两个分析中都包括了肩高。保留了评估性状的四个因子和线性评分性状的 14 个因子，以便进一步分析。在计算因子得分之前，基于相关性状，对具有线性评分性状记录的马的个别性状的缺失值进行了插补，然后使用因子负荷进行了因子得分的计算。使用 BLUPF90 包中的多性状动物模型估计了潜在因子的遗传参数和相关性。遗传力估计值与当前遗传评估中使用的性状相似，范围从 0.05（线性评分性状命名为 L.behaviour 的因子，主要由与行为相关的性状决定）到 0.59（评估性状命名为 E.size 的因子，主要由肩高和 conformation 决定）。对于这两种类型的性状，都为跳跃和步态性状以及体型形成了单独的因子。评估性状和线性评分性状的对应因子之间估计出了高度的遗传相关性。总之，因子分析可用于减少多性状遗传评估或温血马基因组分析中要包含的性状数量。它还可以帮助更好地理解评估性状之间的相互关系，并有助于确定要在多个原始性状的多性状评估中使用的性状子组。
