Author
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Russell, James |
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Submitted to: Journal of Animal Science
Publication Type: Review Article Publication Acceptance Date: 3/11/1998 Publication Date: N/A Citation: N/A Interpretive Summary: Not required. Technical Abstract: When ruminal bacteria have insufficient nitrogen and other nutrients, excess carbohydrate can be toxic. Pure cultures that are nitrogen-limited can only convert some of the excess carbohydrate to intracellular polysaccharide. Fibrobacter succinogenes cultures that have excess-cellobiose secrete glucose and cellotriose into the culture medium, and Prevotella ruminicola produces methylglyoxal, a highly toxic substance that causes a dramatic decrease in viability. Some ruminal bacteria (e.g. Streptococcus bovis and Selenomonas ruminantium) have mechanisms to decrease ATP production or spill the ATP that has already been produced. These mechanisms of decreasing intracellular ATP appear to protect the cell. Most ruminal bacteria can use ammonia as a nitrogen source, but amino nitrogen increases the growth efficiency of mixed ruminal bacteria. Amino-nitrogen dependent improvements in growth efficiency can be explained dby an increase in growth rate and a decrease in energy spilling. Amino nitrogen is only beneficial if the rate of carbohydrate fermentation is rapid and carohydrate is in excess. |
