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Influence of Aureomycin on Rumen Metabolism

Ohio State University, Columbus

Abstract

Metabolism and digestion trials were conducted with seven rumen fistulated wethers. Experimental treatments consisted of (A) control, (B) the infusion of 20 mg. of aureomycin into the rumen via the fistula 90 min. prior to feeding, and (C and D) the addition of 20 and 60 mg. of aureomycin, respectively, to the daily ration. Data from a 4 x 4 Latin square experiment and pooled data from seven animals are presented. Both viable and total bacterial counts indicated that bacterial concentrations did not change significantly throughout the experiment. However, pooled data showed that protozoal concentrations resulting from antibiotic addition in vivo were significantly greater than those in control animals. At the same time apparent nitrogen digestibility was significantly increased by antibiotic addition to the rations. Both the nitrogen balance and urinary nitrogen tended to increase with antibiotic administration. Dry matter digestion was significantly increased when antibiotic was administered.

Gas production in vitro by rumen organisms taken from animals on the respective treatments showed that inhibition by the addition in vitro of antibiotic was significantly greater, when rumen organisms were taken from control lambs than when taken from lambs fed 60 mg. aureomycin. Further, gas production resulting from the addition of nutrients to prefeeding rumen samples was significantly greater with samples from animals receiving 20 mg. aureomycin, either before feeding or with the feed, than with samples from control animals or animals receiving 60 mg. aureomycin with the daily feed. Pooled data showed that gas production in vitro by rumen contents 1 hr. after feeding from animals receiving 20 mg. aureomycin in their ration, was significantly greater than by rumen contents from control animals.

¹ Institute of Nutrition and Food Technology, Ohio State University.

² Department of Animal Science, Ohio State University.