Abstract Context It is believed that the X chromosome plays an important role in influencing quantitative traits. Despite this, until recently, X-linked genetic effects have not been considered in models to estimate genetic parameters for economically important traits of livestock. Aims A large dataset was analysed to quantify autosomal additive genetic, X-linked additive genetic and maternal effects on growth and efficiency-related traits in Baluchi sheep. Methods Traits included bodyweight at birth, weaning (WW), 6 months (W6), 9 months and yearling age, pre- and post-weaning average daily gain, pre- and post-weaning Kleiber ratio, pre- and post-weaning efficiency of growth (EFb), and pre- and post-weaning relative growth rate. Each trait was analysed using the REML procedure fitting a series of eight univariate animal models. For each trait, the most appropriate model was selected by the Akaike information criterion and Bayesian information criterion. Key results The X-linked genetic effect was significant only in models fitted to EFb, where the estimate of X-linked heritability was 0.02 ± 0.01 from the best model. Other traits were not affected significantly by X-linked genetic effects. Estimates of autosomal heritability () for growth traits were between 0.06 ± 0.02 (post-weaning average daily gain, pre-weaning relative growth rate) and 0.22 ± 0.04 (bodyweight at yearling age), and ranged between 0.02 ± 0.01 (EFb) and 0.08 ± 0.02 (pre-weaning Kleiber ratio) for efficiency-related traits. Maternal effects significantly contributed to phenotypic variation of most traits, with larger effects on traits measured early in life. For EFb, the Spearman’s correlation between breeding values including and excluding X-linked effects was 0.95. It was 1.00 for traits that were not affected by X-linked genetic effects. Conclusions Although the proportion of phenotypic variance attributed to X-linked loci for most traits was zero, the importance of X-linked genetic effects should be at least tested in models when estimating variance components for growth and efficiency traits of Baluchi sheep. Implications As estimates of genetic parameters are breed-specific, we recommend for growth and efficiency traits of sheep that the importance of X-linked genetic effects should be evaluated to assess if these effects should be included in models used in genetic evaluation.

中文翻译：

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X染色体和常染色体遗传对绵羊生长和效率相关性状的影响分析

摘要 背景人们认为X染色体在影响数量性状方面起着重要作用。尽管如此，直到最近，还没有在模型中考虑 X 连锁遗传效应来估计牲畜重要经济性状的遗传参数。目的 分析大型数据集以量化常染色体加性遗传、X 连锁加性遗传和母体对俾路支羊生长和效率相关性状的影响。方法 性状包括出生体重、断奶 (WW)、6 个月 (W6)、9 个月和周龄、断奶前后平均日增重、断奶前后 Kleiber 比率、断奶前后效率生长率 (EFb)，以及断奶前和断奶后的相对增长率。使用适合一系列八个单变量动物模型的 REML 程序分析每个性状。对于每个特征，通过 Akaike 信息准则和贝叶斯信息准则选择最合适的模型。主要结果 X 连锁遗传效应仅在拟合 EFb 的模型中显着，其中 X 连锁遗传力的估计值与最佳模型相比为 0.02 ± 0.01。其他性状不受 X 连锁遗传效应的显着影响。生长性状的常染色体遗传力 () 估计值介于 0.06 ± 0.02（断奶后平均日增重、断奶前相对增长率）和 0.22 ± 0.04（周龄体重）之间，范围介于 0.02 ± 0.01 (EFb) 和0.08 ± 0.02（断奶前克莱伯比率）对于效率相关性状。母体效应对大多数性状的表型变异有显着影响，对生命早期测量的性状影响更大。对于 EFb，包括和不包括 X 连锁效应在内的育种值之间的 Spearman 相关系数为 0.95。对于不受 X 连锁遗传效应影响的性状，它是 1.00。结论 尽管大多数性状归因于 X 连锁基因座的表型方差比例为零，但在估计俾路支羊生长和效率性状的方差分量时，至少应在模型中测试 X 连锁遗传效应的重要性。影响 由于遗传参数的估计是品种特异性的，我们建议对于绵羊的生长和效率性状，应评估 X 连锁遗传效应的重要性，以评估这些效应是否应包括在遗传评估中使用的模型中。结论 尽管大多数性状归因于 X 连锁基因座的表型方差比例为零，但在估计俾路支羊生长和效率性状的方差分量时，至少应在模型中测试 X 连锁遗传效应的重要性。影响 由于遗传参数的估计是品种特异性的，我们建议对于绵羊的生长和效率性状，应评估 X 连锁遗传效应的重要性，以评估这些效应是否应包括在遗传评估中使用的模型中。结论 尽管大多数性状归因于 X 连锁基因座的表型方差比例为零，但在估计俾路支羊生长和效率性状的方差分量时，至少应在模型中测试 X 连锁遗传效应的重要性。影响 由于遗传参数的估计是品种特异性的，我们建议对于绵羊的生长和效率性状，应评估 X 连锁遗传效应的重要性，以评估这些效应是否应包括在遗传评估中使用的模型中。