Objective

The present work aimed to obtain common effect sizes for the gene frequency and association of MspI derived variants of growth hormone (GH) gene with milk yield in dairy cows.

Methods

We performed a systematic review and meta-analysis of 35 published studies identified in literature search from 2000 to 2020 (n = 4164). These studies were specific to fragment size (329) for genotypes viz., CC (224, 105 bp), CD (329, 224, 105 bp) and DD (329 bp). Pooled standard mean differences (SMDs) as effect sizes between allele pairs were derived using different genetic models. The heterogeneity between effects sizes across studies was estimated using I² Index (%).

Results

The common effect size for gene frequency of allele C (224, 105 bp) was significantly (P < 0.05) higher in 2881 Bos taurus/cross cows (0.82; 95% CI: 0.74, 0.89; I² = 97.81%) than 1283 Bos indicus cows (0.15; 95% CI: 0.12, 0.18; I² = 71.90%), with overall gene frequency was 0.33 (95% CI: 0.21, 0.46; I² = 99.29%). Additive (CC vs. DD) and dominant (CC + CD vs. DD) did not revealed significant (P > 0.05) association with milk yield. However, completely over dominant (CC + DD vs. CD) and recessive (CC vs. CD + DD) models showed significant (P < 0.05) and positive SMDs with milk yield specially at early lactations. There was no evidence of heterogeneity (I² = 0.00%) between SMDs across studies.

Conclusions

This meta-analysis suggested potential association of C allele for enhancing milk production of dairy cows.

中文翻译：

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MspI衍生的与奶牛产奶量相关的生长激素基因变异的荟萃分析

客观的

目前的工作旨在获得基因频率的共同效应大小以及Msp I 衍生的生长激素 (GH) 基因变体与奶牛产奶量的关联。

方法

我们对 2000 年至 2020 年在文献检索中发现的 35 项已发表研究进行了系统回顾和荟萃分析（n  = 4164）。这些研究特定于基因型的片段大小（329），即。、 CC（224、105 bp）、CD（329、224、105 bp）和 DD（329 bp）。作为等位基因对之间效应大小的合并标准平均差 (SMD) 是使用不同的遗传模型得出的。^{使用 I 2}指数 (%)估计研究中效应大小之间的异质性。

结果

 在 2881头Bos taurus /cross 奶牛中，等位基因 C (224, 105 bp) 基因频率的共同效应大小显着 ( P < 0.05) (0.82; 95% CI: 0.74, 0.89; I ²  = 97.81%) 高于 1283 Bos indicus奶牛 (0.15; 95% CI: 0.12, 0.18; I ²  = 71.90%), 总基因频率为 0.33 (95% CI: 0.21, 0.46; I ²  = 99.29%)。 添加剂（CC vs. DD）和显性（CC + CD vs. DD）与产奶量没有显着关联（P > 0.05）。然而，完全超显性（CC + DD vs. CD）和隐性（CC vs. CD + DD）模型显示出显着（P < 0.05) 和阳性 SMD，尤其是在泌乳早期。没有证据表明跨研究的 SMD 之间存在异质性 (I ²  = 0.00%)。

结论

该荟萃分析表明 C 等位基因与提高奶牛产奶量的潜在关联。