Centre for Integrative Genetics, Norwegian University of Life Sciences, N-1432 Aas, Norway.
Anim Genet. 2011 Oct;42(5):466-74. doi: 10.1111/j.1365-2052.2011.02179.x. Epub 2011 Mar 13.
Reproductive performance is a critical trait in dairy cattle. Poor reproductive performance leads to prolonged calving intervals, higher culling rates and extra expenses related to multiple inseminations, veterinary treatments and replacements. Genetic gain for improved reproduction through traditional selection is often slow because of low heritability and negative correlations with production traits. Detection of DNA markers associated with improved reproductive performance through genome-wide association studies could lead to genetic gain that is more balanced between fertility and production. Norwegian Red cattle are well suited for such studies, as very large numbers of detailed reproduction records are available. We conducted a genome-wide association study for non-return rate, fertility treatments and retained placenta using almost 1 million records on these traits and 17 343 genome-wide single-nucleotide polymorphisms. Genotyping costs were minimized by genotyping the sires of the cows recorded and by using daughter averages as phenotypes. The genotyped sires were assigned to either a discovery or a validation population. Associations were only considered to be validated if they were significant in both groups. Strong associations were found and validated on chromosomes 1, 5, 8, 9, 11 and 12. Several of these were highly supported by findings in other studies. The most important result was an association for non-return rate in heifers in a region of BTA12 where several associations for milk production traits have previously been found. Subsequent fine-mapping verified the presence of a quantitative trait loci (QTL) having opposing effects on non-return rate and milk production at 18 Mb. The other reproduction QTL did not have pleiotropic effects on milk production, and these are therefore of considerable interest for use in marker-assisted selection.
繁殖性能是奶牛的一个重要特征。繁殖性能差会导致产犊间隔延长、淘汰率增加，以及多次授精、兽医治疗和更换所带来的额外费用。通过传统选择提高繁殖性能的遗传进展通常较慢，因为遗传力低且与生产性状呈负相关。通过全基因组关联研究检测与提高繁殖性能相关的 DNA 标记，可以带来更平衡的繁殖力和生产性能的遗传进展。挪威红牛非常适合进行这样的研究，因为有大量详细的繁殖记录可供使用。我们使用近 100 万份关于这些性状的记录和 17343 个全基因组单核苷酸多态性，对返情率、受精处理和胎衣不下进行了全基因组关联研究。通过对记录牛的公牛进行基因分型，并使用女儿平均值作为表型，最大限度地降低了基因分型成本。所鉴定的公牛被分配到发现群体或验证群体中。只有在两个群体中都显著的关联才被认为是有效的。在染色体 1、5、8、9、11 和 12 上发现并验证了强烈的关联。其中一些在其他研究中得到了强有力的支持。最重要的结果是在 BTA12 上发现了一个与小母牛返情率相关的区域，该区域先前已经发现了多个与产奶量性状相关的关联。随后的精细定位证实了在 18Mb 处存在一个对返情率和产奶量有相反影响的数量性状位点（QTL）。其他的繁殖 QTL 对产奶量没有多效性，因此它们在标记辅助选择中具有相当大的应用价值。
