Urea nitrogen induces changes in rumen microbial and host metabolic profiles in dairy cows
Urea nitrogen induces changes in rumen microbial and host metabolic profiles in dairy cows
复制标题
尿素氮诱导奶牛瘤胃微生物和宿主代谢特征的变化
DOI：
10.1016/j.livsci.2018.02.011
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发表时间：
2018-04-01
影响因子：
1.8
通讯作者：
Wang, J. Q.
中科院分区：
文献类型：
--
作者：
Jin, D.;Zhao, S. G.;Wang, J. Q.
尿素作为一种非蛋白质氮源已被应用于牛日粮中。水解成氨，可用于微生物蛋白质的合成。利用代谢组学方法研究尿素氮诱导的瘤胃微生物和宿主血液代谢谱的研究尚未得到证实。本研究的目的是利用基于核磁共振（NMR）的非靶向定量代谢组学方法，确定奶牛补充尿素后瘤胃微生物和血浆代谢物谱的变化。选取6头瘤胃瘘管奶牛，随机分为2组，进行2期交叉试验，每组21 d。试验期内，所有奶牛均饲喂相同的全混合日粮，但每头奶牛每日在饲粮中添加或不添加180 g尿素。采集瘤胃液和血液样本，采用核磁共振波谱和多变量方差分析进行分析。采用正交偏最小二乘判别分析评估两组奶牛瘤胃和血浆代谢物浓度的差异，并通过检索相关数据库进行鉴定。尿素添加组瘤胃中缬氨酸、天冬氨酸、谷氨酸和尿嘧啶浓度以及血浆中尿素和焦谷氨酸浓度均高于对照组（P < 0.05）。代谢途径分析显示，尿素氮显著提高了瘤胃泛酸和辅酶a的生物合成、β -丙氨酸代谢、缬氨酸、亮氨酸和异亮氨酸代谢以及血浆尿素和谷胱甘肽代谢。瘤胃天冬氨酸和谷氨酸水平与血浆尿素水平呈极显著正相关（P < 0.01）。这些发现提供了新的信息，有助于理解尿素氮对奶牛代谢途径的影响，并可能有助于指导提高瘤胃尿素利用率的努力。
Urea has been used in diets of cattle as a non-protein nitrogen source. It is hydrolyzed to ammonia, which can be used for microbial protein synthesis. Use of metabolomics methodologies to study the rumen microbial and host blood metabolic profiles induced by urea nitrogen has not been previously characterized. The objective of this study was to identify changes in rumen microbial and plasma metabolite profiles in dairy cows after urea supplementation using a nuclear magnetic resonance (NMR)-based untargeted quantitative metabolomic approach. Six dairy cows with rumen fistulas were randomly assigned to two groups used in a two period crossover trial and each experimental period lasted 21 days. All the cows were fed the same total mixed rations, but were intraruminally supplemented with 180 g urea per cow daily or not during the experimental period. Rumen fluid and blood samples were collected and analyzed using nuclear magnetic resonance spectroscopy and multivariate analysis of variance. Differences in rumen and plasma metabolite concentrations in cows from the two groups were assessed using orthogonal partial least-squares discriminant analysis and identified by searching against related databases. Concentrations of valine, aspartate, glutamate, and uracil in the rumen, and urea and pyroglutamate in the plasma, were higher (P < 0.05) in the urea-supplemented group than in the control group. Metabolic pathway analysis of the affected metabolites revealed that pantothenate and CoA biosynthesis, beta-alanine metabolism, valine, leucine, and isoleucine metabolism in the rumen, and urea and glutathione metabolism in the plasma were significantly increased by urea nitrogen. The levels of aspartate and glutamate in the rumen correlated strongly (P < 0.01) with the level of urea in plasma. These findings provided novel information to aid understanding of the metabolic pathways affected by urea nitrogen in dairy cows, and could potentially help to guide efforts directed at improving the efficiency of urea utilization in the rumen.