The Effect of Antibiotics upon the Digestion of Feed Nutrients by Yearling Steers, with Bacteriological Data

Abstract

Aureomycin and penicillin at different levels of intake were compared in digestion and nitrogen balance trials with steers. The results indicated (1) that aureomycin had a greater depressing effect than penicillin on the digestibility of protein and crude fiber, and (2) that the two supplements had about equal effect in decreasing nitrogen retention. Penicillin fed at the rate of 100 mg. per day did not appear to upset the rumen flora and environment; whereas, 100 mg. of aureomycin resulted in a less desirable rumen flora for roughage digestion, the flora showing a decreased ability to digest fiber in the miniature artificial rumen.