Subclinical metabolic disorders such as ketosis cause substantial economic losses for dairy farmers in addition to the serious welfare issues they pose for dairy cows. Major hurdles in genetic improvement against metabolic disorders such as ketosis include difficulties in large-scale phenotype recording and low heritability of traits. Milk concentrations of ketone bodies, such as acetone and β-hydroxybutyric acid (BHB), might be useful indicators to select cows for low susceptibility to ketosis. However, heritability estimates reported for milk BHB and acetone in several dairy cattle breeds were low. The rumen microbial community has been reported to play a significant role in host energy homeostasis and metabolic and physiologic adaptations. The current study aims at investigating the effects of cows' genome and rumen microbial composition on concentrations of acetone and BHB in milk, and identifying specific rumen microbial taxa associated with variation in milk acetone and BHB concentrations. We determined the concentrations of acetone and BHB in milk using nuclear magnetic resonance spectroscopy on morning milk samples collected from 277 Danish Holstein cows. Imputed high-density genotype data were available for these cows. Using genomic and microbial prediction models with a 10-fold resampling strategy, we found that rumen microbial composition explains a larger proportion of the variation in milk concentrations of acetone and BHB than do host genetics. Moreover, we identified associations between milk acetone and BHB with some specific bacterial and archaeal operational taxonomic units previously reported to have low to moderate heritability, presenting an opportunity for genetic improvement. However, higher covariation between specific microbial taxa and milk acetone and BHB concentrations might not necessarily indicate a causal relationship; therefore further validation is needed before considering implementation in selection programs.

中文翻译：

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宿主遗传学和瘤胃微生物组对亚临床酮症的预测能力。

亚临床代谢疾病（例如酮病）除了给奶牛带来严重的福利问题外，还给奶农带来了巨大的经济损失。针对诸如酮症等代谢性疾病进行遗传改良的主要障碍包括大规模表型记录的困难和性状的遗传力低。牛奶中酮体（例如丙酮和β-羟基丁酸（BHB））的浓度可能是选择奶牛的低酮症敏感性指标。但是，报告的几种奶牛品种的牛奶BHB和丙酮的遗传力估计值很低。据报道，瘤胃微生物群落在宿主能量稳态，代谢和生理适应中起重要作用。目前的研究旨在调查奶牛的影响 牛奶中丙酮和BHB浓度的基因组和瘤胃微生物组成，并确定与牛奶丙酮和BHB浓度变化相关的特定瘤胃微生物分类群。我们使用核磁共振波谱法对从277头丹麦荷斯坦奶牛采集的早晨牛奶样品进行了核磁共振波谱测定，确定了牛奶中丙酮和BHB的浓度。这些奶牛可获得估算的高密度基因型数据。使用具有10倍重采样策略的基因组和微生物预测模型，我们发现瘤胃微生物成分比宿主遗传学解释了更大比例的丙酮和BHB牛奶浓度变化。此外，我们确定了牛奶丙酮和BHB与某些特定的细菌和古细菌操作分类单位之间的关联，这些单位先前据报道具有较低至中等的遗传力，为遗传改良提供了机会。但是，特定微生物分类群与牛奶丙酮和BHB浓度之间的较高协变可能未必表明存在因果关系。因此，在考虑在选择程序中实施之前，需要进行进一步的验证。