A Quantitative Study of Rumen Synthesis in the Bovine on Natural and Purified Rations I. Protein, Dry Matter and Non-Protein Nitrogen

Abstract

Seven balance trials were conducted with three rumenfistulated calves maintained on a purified ration in which urea furnished the only source of dietary nitrogen and one trial was conducted with one calf maintained on a natural ration, to determine the rate of disappearance of dry matter and nonprotein nitrogen from the rumen and to study the biosynthesis of protein. The entire rumen contents were evacuated, weighed, sampled and replaced in the rumen both before and 6 hours after feeding. On a percentage basis, rumen dry matter and non-protein nitrogen increased appreciably within 6 hours after feeding, but crude protein increased in only 4 of 7 trials. The rate of removal of dry matter was approximately the same irrespective of the ration fed (approximately 60%), and 90% of the non-protein nitrogen had disappeared from the rumen within 6 hours after feeding. The data indicate an appreciable synthesis of protein from urea in the bovine rumen within 6 hours after feeding. In 7 trials, the amount of “true” protein synthesized varied from 33 to 109 gm. The increase in protein is assumed to be due to the biosynthetic activity of rumen microorganisms.