Rumen Synthesis of the Vitamin B Complex as Influenced by Ration Composition

The addition of urea as a source of nitrogen definitely increased the synthesis of riboflavin, nicotinic acid, biotin and pantothenic acid in the bovine rumen when a readily available carbohydrate was present. Pyridoxine and “folic acid” could not be too closely correlated with ration composition. In the absence of a readily fermentable carbohydrate and probably a low population of microorganisms the synthesis of the members of the B complex is not at a maximum. The data indicate that thiamine may not be synthesized in the rumen. However, it seems more than probable that it is synthesized, but absorbed or destroyed at a rate greater than its synthesis.