Roman L. Hruska US Meat Animal Research Center, USDA-ARS, Clay Center, NE 68933, USA.
J Anim Sci. 2012 Jul;90(7):2142-51. doi: 10.2527/jas.2011-4536. Epub 2012 Mar 9.
Reproductive efficiency is of economic importance in commercial beef cattle production, since failure to achieve pregnancy reduces the number of calves marketed. Identification of genetic markers with predictive merit for reproductive success would facilitate early selection of females and avoid inefficiencies associated with sub-fertile cows. To identify regions of the genome harboring variation affecting reproductive success, we applied a genome-wide association approach based on the >700,000 SNP marker assay. To include the largest number of individuals possible under the available budget, cows from several populations were assigned to extremes for reproductive efficiency, and DNA was pooled within population and phenotype before genotyping. Surprisingly, pools prepared from DNA of low reproductive cattle returned fluorescence intensity data intermediate between fertile females and males for SNP mapped to the Y chromosome (i.e., male sex chromosome). The presence of Y-associated material in low reproductive heifers or cows was confirmed by Y-directed PCR, which revealed that 21 to 29% of females in the low reproductive category were positive by a Y chromosome PCR test normally used to sex embryos. The presence of the Y chromosome anomaly was further confirmed with application of additional Y-specific PCR amplicons, indicating the likelihood of the presence of some portion of male sex chromosome in female cattle in various beef cattle herds across the U.S. Discovery of this Y anomaly in low reproductive females may make an important contribution to management of reproductive failures in beef cattle operations.
繁殖效率在商业肉牛生产中具有经济重要性，因为妊娠失败会减少销售的小牛数量。鉴定具有预测生殖成功价值的遗传标记将有助于早期选择雌性动物，并避免与低生育率奶牛相关的效率低下。为了确定影响繁殖成功的基因组区域，我们应用了基于 >700,000 SNP 标记分析的全基因组关联方法。为了在可用预算内尽可能多地包括个体，来自多个群体的奶牛被分配到繁殖效率的极端，并且在基因分型之前在群体内和表型内对 DNA 进行了混合。令人惊讶的是，从繁殖能力低的奶牛的 DNA 制备的池返回的荧光强度数据介于可育雌性和雄性之间，这些 SNP 映射到 Y 染色体（即，雄性性染色体）。通过 Y 定向 PCR 证实了低繁殖小母牛或奶牛中存在 Y 相关物质，该 PCR 揭示了低繁殖类别中的 21%至 29%的雌性通过通常用于胚胎性别鉴定的 Y 染色体 PCR 测试呈阳性。通过应用其他 Y 特异性 PCR 扩增子进一步证实了 Y 染色体异常的存在，表明在美国各地的各种肉牛群中，雌性牛中存在部分雄性性染色体的可能性。在低繁殖雌性中发现这种 Y 异常可能会对肉牛生产中繁殖失败的管理做出重要贡献。
