A meta-analysis on the effects of A and B alleles, the most frequent alleles of CSN3 gene, on milk yield and composition traits was conducted by pooling a large dataset consisting of 30 471 genotyped cattle. Four genetic models, comprising dominant (AA + AB vs. BB), recessive (AA vs. AB + BB), additive (AA vs. BB) and co-dominant (AA + BB vs. AB), were employed to analyze data. Standardized mean difference (SMD) was used to measure the size of the effects of A and B alleles of CSN3 on studied traits. Effect sizes of 0.2, 0.5 and 0.8 represent small, medium and large effects, respectively. The results indicate that B allele, in the form of BB genotype, has a significant, but medium effect on lactation yield under dominant (SMD = 0.259, P-value = 0.006) and additive (SMD = 0.279, P-value = 0.035) models. Moreover, a small decrease in the fat percentage occurred in cows having A allele under dominant (SMD = -0.077, P-value = 0.006) and additive (SMD = -0.106, P-value = 0.035) models. Furthermore, CSN3 variants significantly but slightly affect protein percentage under dominant (SMD = -0.146, P-value = 0.000), recessive (SMD = -0.077, P-value = 0.000) and additive (SMD = -0.219, P-value = 0.000) models, showing the negative effect of A allele on this trait. Meta-analysis results reveal that daily milk yield is slightly affected by CSN3 variants under recessive (SMD = 0.056, P-value = 0.033) and additive (SMD = 0.061, P-value = 0.013) genetic models. There is no effect of CSN3 variants on either protein or fat yield. In addition, the effects of CSN3 variants on milk-related traits were not observed under the co-dominant model. Sensitivity and publication bias analyses were carried out to confirm the stability of meta-analyses results.

中文翻译：

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对牛CSN3基因变异与牛奶产量和组成之间关联的荟萃分析。

通过汇总由30 471个基因型牛组成的大型数据集，对CSN3基因最常见的A和B等位基因对牛奶产量和组成性状的影响进行了荟萃分析。四个遗传模型用于分析数据，包括显性（AA + AB vs. BB），隐性（AA vs. AB + BB），加性（AA vs. BB）和共显性（AA + BB vs. AB）。 。使用标准化平均差异（SMD）来衡量CSN3的A和B等位基因对所研究性状的影响的大小。0.2、0.5和0.8的效果大小分别表示小，中和大效果。结果表明，以BB基因型形式存在的B等位基因在显性（SMD = 0.259，P值= 0.006）和加性（SMD = 0.279，P值= 0.035）下对泌乳产量有显着但中等的影响楷模。此外，在A等位基因处于显性（SMD = -0.077，P值= 0.006）和加性（SMD = -0.106，P值= 0.035）模型的奶牛中，脂肪百分比略有下降。此外，CSN3变体在显性（SMD = -0.146，P值= 0.000），隐性（SMD = -0.077，P值= 0.000）和加性（SMD = -0.219，P值= 0.000）模型，显示A等位基因对该性状的负面影响。荟萃分析结果显示，在隐性（SMD = 0.056，P值= 0.033）和加性（SMD = 0.061，P值= 0.013）遗传模型下，CSN3变异对日乳产量有轻微影响。CSN3变体对蛋白质或脂肪产量没有影响。另外，在共显性模型下未观察到CSN3变体对牛奶相关性状的影响。