Department of Biological and Computing Sciences, University of Alberta, Edmonton, AB, Canada TG6 2P5.
J Dairy Sci. 2012 Nov;95(11):6606-23. doi: 10.3168/jds.2012-5403. Epub 2012 Sep 7.
Dairy cows fed high-grain diets during early lactation have a high incidence of metabolic disorders. However, the precise mechanism(s) of how grain feeding causes disease is not clear. In an effort to understand how this diet transition alters the rumen environment and potentially leads to certain metabolic disorders in dairy cattle, we undertook a comprehensive, quantitative metabolomic analysis of rumen fluid samples from dairy cows fed 4 different diets. Using a combination of proton nuclear magnetic resonance spectroscopy, gas chromatography-mass spectrometry, and direct flow injection tandem mass spectroscopy, we identified and quantified 93 metabolites in rumen samples taken from 8 dairy cows fed graded amounts of barley grain (i.e., 0, 15, 30, and 45% of diet dry matter). We also studied temporal changes in the rumen by studying metabolite concentration differences between the first day and the last day of each diet phase following the diet adaptation period. Multivariate analysis showed that rumen metabolites arising from the diet containing 45% barley grain were clearly different from those containing 0, 15, and 30% barley grain. Likewise, a clear separation of the metabolic composition of the ruminal fluid was evident at the beginning and at the end of each diet phase-contrary to the belief that 11 d are suitable for the adaptation of cows to high-grain diets. High-grain diets (>30%) resulted in increased rumen fluid concentrations of several toxic, inflammatory, and unnatural compounds including putrescine, methylamines, ethanolamine, and short-chain fatty acids. Perturbations in several amino acids (phenylalanine, ornithine, lysine, leucine, arginine, valine, and phenylacetylglycine) were also evident. The present study confirms and greatly extends earlier observations on dietary effects on rumen fluid composition and shows that the use of multiple metabolomic platforms permits a far more detailed understanding of metabolic causes and effects. These results may improve our understanding of diet-related rumen metabolism and the influence of grain on the overall health of dairy cattle.
奶牛在泌乳早期饲喂高谷物日粮会发生多种代谢紊乱。然而，谷物喂养导致疾病的确切机制尚不清楚。为了了解这种饮食转变如何改变瘤胃环境，并可能导致奶牛发生某些代谢紊乱，我们对饲喂 4 种不同日粮的奶牛的瘤胃液样本进行了全面、定量的代谢组学分析。我们使用质子核磁共振波谱、气相色谱-质谱联用和直接流动注射串联质谱联用技术，鉴定并定量分析了 8 头奶牛的瘤胃液样本中的 93 种代谢物，这些奶牛的日粮中分别含有 0、15、30 和 45%（干物质基础）的大麦。我们还通过研究每个日粮阶段适应期后第 1 天和最后 1 天瘤胃液代谢物浓度差异来研究瘤胃的时间变化。多变量分析表明，含有 45%大麦的日粮产生的瘤胃代谢物与含有 0、15 和 30%大麦的日粮产生的代谢物明显不同。同样，在每个日粮阶段的开始和结束时，瘤胃液的代谢组成明显分离——这与人们认为奶牛适应高谷物日粮需要 11 天的观点相反。高谷物日粮（＞30%）导致瘤胃液中几种毒性、炎症和非天然化合物的浓度升高，包括腐胺、甲基胺、乙醇胺和短链脂肪酸。几种氨基酸（苯丙氨酸、精氨酸、赖氨酸、亮氨酸、精氨酸、缬氨酸和苯乙酰甘氨酸）的含量也发生了明显变化。本研究证实并大大扩展了以前关于日粮对瘤胃液组成影响的观察结果，并表明使用多种代谢组学平台可以更详细地了解代谢的因果关系。这些结果可能有助于我们更好地理解与饮食相关的瘤胃代谢以及谷物对奶牛整体健康的影响。
