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United States Department of Agriculture

Agricultural Research Service

Title: Accessibility of Ruminal Cellulolytic Bacteria to Cellulose and Its Role in Limiting Forage Fiber Digestion

Author
item Weimer, Paul

Submitted to: Food Structure
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 26, 1996
Publication Date: N/A

Interpretive Summary: Forage cell walls can be digested by ruminant animals only if they are physically accessible to the rumen microorganisms. Although microbes are small, they normally can gain access to only a small fraction of the digestible feed materials at any one time. Several lines of evidence suggest that certain plant cell types may owe their poor digestibility to anatomical structures that limit microbial accessibility. A new method, based on the solute exclusion technique for analyzing wood fibers, is presented for measuring the ability of microbes to penetrate into the digestible regions of these cells. This method will allow us to determine if the slow digestion of these plant cell walls is due to a slow penetration of the microbes to the site of digestion.

Technical Abstract: Plant cell walls are composed of a complex matrix of polysaccharides intimately associated with lignin and phenolic acids. Physical intercalation and chemical crosslinking of these components represent a major limitation to forage fiber digestion. Additional constraints are provided by the structural properties of the polysaccharides themselves (particularly cellulose), and by certain adaptive features of the ruminal cellulolytic bacteria that enhance their ability to digest cellulose, but limit their ability to gain access to it. A new method, based on the solute exclusion technique for characterizing the pore volume distribution of wood fibers, is presented for measuring the ability of microbes to penetrate by passive diffusion into the digestible regions of these cells.

Last Modified: 11/23/2014
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