Skip to main content
ARS Home » Research » Publications at this Location » Publication #67153


item Hespell, Robert
item Akin, Danny

Submitted to: Book Chapter in Ecology and Physiology
Publication Type: Book / Chapter
Publication Acceptance Date: 6/1/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: An interpretive summary is not required for a literature review, book chapter (unless reporting original research), book review, or oral presentation (where only the title or abstract is published. Refer to directive 152.1 4/3/91

Technical Abstract: In ruminants, an extensive microbial fermentation of ingested food occurs in the foregut sac called the rumen. Much of the food is converted by the microbial population into volatile fatty acids, microbial cells, and vitamins, providing the host animal with most of its nutritional requirements. The ruminal microbial population is very dense, consisting of about 10**10 bacteria/ml, 10**6/ml protozoa, and 10**3 to 10**7 fungi/ml. Ruminal environment is strictly anaerobic, buffered in the range pH 5.7 to 7.3 by saliva-derived bicarbonate and microbial carbon dioxide production, and the fermenting contents are held in the range of 36 to 41 C. As will be discussed in the following sections, the ruminal microorganisms are well adapted to grow in this environment and many of their growth requirements reflect the availability and types of nutritional factors present in ruminal fluid. The microbial population has wide diversity in species and in their metabolic abilities to carry out processes such as hydrolysis of cellulose, xylans, proteins, fermentation of sugars, or hydrogenation of fatty acids. As a consequence of this diversity, the host animal can utilize and switch quickly to many types of plant materials for food. The effects of diet on changes in bacteria, protozoa, fungi, or other microbial changes as well as descriptions of the morphologies, nutritional aspects, and major functional roles of various microbial species in the rumen will be discussed in this chapter.