Antibiotics in Rumen Digestion and Synthesis. I. The Effect of Aureomycin on Rumen Digestion and the Passage of Nutrients from the Rumen during Specific Intervals after Feeding

Abstract

Two rumen-fistulated steers were used to study the influence of aureomycin on rumen digestion and the rate of passage of certain nutrients from the rumen. Aureomycin was fed at the rate of 0.5 g./day for 15 days and then 1 g./day for the next 15 days. The period in which the steers received no aureomycin served as the control period. Neither of the steers showed signs of anorexia or diarrhea at any time during aureomycin supplementation. The rumen contents were completely evacuated, weighed, sampled and replaced in the rumen before feeding (0-hr.) and again at 6 and 12 hrs. after feeding. The rate of removal of dry matter, crude fiber, crude protein and N-free extract was the highest when 0.5 g. of aureomycin was fed. There was an accumulation of dry matter, crude protein, and N-free extract in the rumen at the 0-hr. period when 1 g. of aureomycin was included in the ration, which suggested that a slight depression in the digestibility of these constituents may have occurred. Ether extract accumulated in the rumen at the 0-hr. period when aureomycin was included in the ration at either level.