Ruminant animals are able to convert plant materials (grain and the human-indigestible portion of carbohydrates) to milk and meat. In this conversion, most of the plant materials are digested by rumen fermentation and are changed to short-chain fatty acids, microbial cells, and methane, which is released into the atmosphere. The relationships among feed, rumen fermentation, and milk production are poorly understood. Here we report a novel indicator of characteristics of rumen fermentation, theoretical turnover rate (TTOR) of the rumen liquid fraction. The TTOR was calculated from the presumed rumen volume (PRV) which is estimated by dividing the methane yield by the methane concentration of rumen fluid. The formula for the TTOR is: TTOR = PRV/body weight0.75 . Our present analyses confirm that the TTOR as an indicator is capable of connecting feed, rumen fermentation, and milk production, because dry matter intake/TTOR showed a strong correlation with milk yield/TTOR. In addition, the TTOR may be related to ruminal pH, as we observed that the ruminal pH decreased as the TTOR increased. We propose that the TTOR is a factor characterizing rumen fermentation and a good indicator of the productivity of ruminants and dysbiosis of the rumen microbiome.

中文翻译：

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奶牛瘤胃液部分的理论周转率及其与采食量，瘤胃发酵和产奶量的关系。

反刍动物能够将植物材料（谷物和人类不易消化的碳水化合物部分）转化为牛奶和肉类。在这种转化过程中，大多数植物材料都经过瘤胃发酵消化，并转变为短链脂肪酸，微生物细胞和甲烷，然后释放到大气中。饲料，瘤胃发酵和产奶量之间的关系知之甚少。在这里，我们报告了瘤胃发酵特性的新指标，瘤胃液体部分的理论周转率（TTOR）。根据假定的瘤胃体积（PRV）计算TTOR，该瘤胃体积通过将甲烷产量除以瘤胃液的甲烷浓度估算得出。TTOR的公式为：TTOR = PRV /体重0.75。我们目前的分析证实，TTOR作为指标可以连接饲料，瘤胃发酵和牛奶产量，因为干物质摄入量/ TTOR与牛奶产量/ TTOR密切相关。此外，TTOR可能与瘤胃pH值有关，因为我们观察到瘤胃pH值随TTOR的增加而降低。我们认为，TTOR是表征瘤胃发酵的一个因素，是反刍动物生产力和瘤胃微生物组营养不良的良好指标。