Mackie R I, White B A
Department of Animal Sciences, University of Illinois, Urbana-Champaign 61801.
J Dairy Sci. 1990 Oct;73(10):2971-95. doi: 10.3168/jds.S0022-0302(90)78986-2.
Feedstuffs consumed by ruminants are all initially exposed to fermentative activity in the rumen prior to gastric and intestinal digestion. The extent and type of transformation of feedstuffs thus determines the productive performance of the host. Research on rumen microbial ecology and metabolism is essentially a study of the interactions between the host, microorganisms present, substrates available, and end products of digestion. Furthermore, the interactions of the normal microbial flora with the host can be manipulated to improve the efficiency of nutrient utilization in ruminant animals. Three important areas of ruminal fermentation will be reviewed, N metabolism, fiber degradation, and biotransformation of toxic compounds. The extent of protein degradation and the rate of uptake of resultant peptides and ammonia are extremely important factors in determining the efficiency of N utilization by rumen bacteria and, therefore, the relative amounts of microbial or bypass protein available to the host. Strategies aimed at identifying and characterizing rate-limiting enzymes of cellulolytic bacteria are essential in elucidating mechanisms involved in ruminal fiber degradation. Results obtained with ruminococci will be described. The detoxification of phytotoxins by passage through the gastrointestinal tract of ruminants is a process deserving special attention and several examples will be presented. Opportunities for manipulation of rumen fermentation are good. However, successful manipulation and full exploitation depend on a through understanding of the mechanisms involved.
反刍动物所消耗的饲料在进行胃肠消化之前，首先都要在瘤胃中经历发酵活动。饲料转化的程度和类型决定了宿主的生产性能。瘤胃微生物生态学和代谢的研究本质上是对宿主、现存微生物、可用底物以及消化终产物之间相互作用的研究。此外，正常微生物区系与宿主之间的相互作用可以通过调控来提高反刍动物营养物质的利用效率。本文将综述瘤胃发酵的三个重要领域：氮代谢、纤维降解以及有毒化合物的生物转化。蛋白质降解的程度以及由此产生的肽和氨的吸收速率，是决定瘤胃细菌氮利用效率的极其重要的因素，因此也是宿主可利用的微生物蛋白或过瘤胃蛋白相对数量的重要因素。旨在鉴定和表征纤维素分解菌限速酶的策略对于阐明瘤胃纤维降解机制至关重要。本文将介绍瘤胃球菌的相关研究结果。反刍动物胃肠道对植物毒素的解毒过程值得特别关注，文中将给出几个例子。调控瘤胃发酵的机会很多。然而，成功的调控和充分利用取决于对相关机制的透彻理解。
