Further Studies on Riboflavin and Thiamine in the Rumen Content of Cattle. II

Abstract

The data presented show that riboflavin is synthesized in the rumen of the steer when a ration containing corn, alfalfa hay, and a protein supplement is fed. When corn was omitted from the alfalfa hay-protein supplement rations there was no apparent synthesis of riboflavin as judged by the comparative riboflavin content of the ration and the dried ingesta. As the amount of corn in the ration increased, there was a corresponding increase in the riboflavin content of the ingesta. Additional evidence was obtained that when ground corn was fed, the riboflavin content of the ingesta was higher than that of the ingesta from a similar ration containing an equal weight of whole corn. The results with a partially synthetic low-vitamin ration also show that riboflavin is synthesized in the rumen and that there appears to be a correlation between the amount of carbohydrates in the ration and the riboflavin content of the dried ingesta. There was no evidence obtained that thiamine was synthesized in any of the experiments as judged by the comparative thiamine content of the feeds and the dried ingesta, with the possible exception of the one in which ground corn was fed. The results with both whole corn as part of the ration and with the partially synthetic low-vitamin ration show that there was a loss of thiamine in the ingesta in comparison with the feed, but the loss incurred decreased as the amount of corn or carbohydrates in the rations increased.