Effect of Antibiotics on Some Rumen and Intestinal Bacteria

Abstract

ANTIBIOTICS have been for some time added to ruminant feeds to increase the weight gains of the animals and they have also been advocated as remedies for bloat¹. Some workers have also used antibiotics as additions to in vitro experiments on the basis that this would suppress the activities of the bacteria in mixed rumen contents and that residual enzyme activity would be caused by protozoa. (See, for example, ref. 2.) Antibiotics have also been used regularly to suppress bacterial growths in the in vitro culture of protozoa³. Little has, however, been done to test the susceptibility to antibiotics of defined strains of rumen bacteria, especially the strictly anaerobic types. Such anaerobic types have also been found in the intestines of ruminants and non-ruminants.