Ruminants bacterial synthesis

Ruminant animals obtain their B12 from bacterial synthesis that takes place in the rumen. As a result, these animals may suffer from vitamin B12 deficiency when they are grazed on cobalt-deficient pastures because the rumen bacteria will be unable to produce the vitamin. 

When considering sources of niacin, it should be noted that niacin can be, and is, synthesized by the intestinal flora. However, the amount produced is only of minor importance in the human. By contrast, as with thiamin and riboflavin, ruminants (cattle, sheep, etc.) have no dietary requirements for niacin because of bacterial synthesis in the rumen. 

The contribution of the gut flora to the available pantothenate for humans is unknown, but there is some evidence that bacterial synthesis of the vitamin may be important in animals, especially ruminants, since severe deficiency can only be achieved by using antibiotics or antagonists. Clinical conditions such as ulcers or colitis can adversely affect pantothenate status and excretion rates, and dietary fiber may affect its absorption. 

A completely independent study implicating the intestinal bacteria was that of Theiler and his associates (13) in ruminant animals. In the attempt to reproduce experimentally a South African paralytic disease known as lamzietke they fed cattle an experimental diet deficient in vitamin B and noted that evidences of deficiency failed to develop although pigeons on the same diet developed polyneuritis promptly. They assumed that either the vitamin requirement of cattle was extremely low or that it had been satisfied by bacterial synthesis in the intestinal tract the latter explanation seemed the more probable. 

As investigations have revealed the mechanisms of rumen digestion, attempts have been made to alter the patterns of digestion in ways that should improve the nutrition of ruminants. The primary approach has been to modify the microbial population in order to suppress undesirable processes (e.g. methane production see Section 8.4 and Chapter 11) or stimulate desirable processes (e.g. microbial protein synthesis). A secondary approach has been to protect nutrients from rumen fermentation in order that they should be digested in the small intestine. Changing the bacterial... 

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