Abstract：
In this paper, we present a comprehensive study of gestation length (GL) in 16 cattle breeds by using large genotype and animal record databases. Data included over 20 million gestations since 2000 and genotypes from one million calves. The study addressed the GL variability within and between breeds, estimation of its direct and maternal heritability coefficients, association with fitness and several economic traits, and QTL detection. The breed average GL varied from 279.7 to 294.4 d, in Holstein and Blonde d\'Aquitaine breeds, respectively. Standard deviations per breed were similar and ranged from 5.2 to 5.8 d. Direct heritability (i.e., for GL defined as a trait of the calf) was moderate to high (h2 = 0.40 to 0.67), whereas the maternal heritability was low (0.04 to 0.06). Extreme breeding values for GL were strongly associated with a higher mortality during the first 2 d of life and were associated with milk production of dams for dairy breeds and precocity of females. Finally, several QTL were detected affecting GL with cumulated effects up to a few days, and at least 2 QTL were found to be shared between different breeds. Our study highlights the risks that would be associated with selection toward a reduced gestation length. Further genomic studies are needed to identify the causal variants, and their association with juvenile mortality and other economic traits.
摘要：
在本文中,我们通过使用大型基因型和动物记录数据库，对16个牛品种的妊娠长度（GL）进行了全面研究。数据包括自2000年以来的2000多万例妊娠和100万头小牛的基因型。这项研究解决了品种内部和品种之间的GL变异性，估计其直接和母体遗传力系数，与健身和几个经济特征有关，和QTL检测。品种平均GL从279.7到294.4d不等，在荷斯坦和金发碧眼的阿基坦品种中，分别。每个品种的标准偏差相似，范围为5.2至5.8d。直接遗传力(即，对于定义为小牛性状的GL)是中等到高(h2=0.40到0.67)，而母亲的遗传力较低（0.04至0.06）。GL的极端育种值与生命的前2天的较高死亡率密切相关，并且与乳品品种的水坝产奶量和雌性早熟有关。最后,检测到几个影响GL的QTL，累积效应长达几天，发现至少2个QTL在不同品种之间共享。我们的研究强调了与选择减少妊娠长度相关的风险。需要进一步的基因组研究来确定因果变异，以及它们与青少年死亡率和其他经济特征的关系。
