Effect of Coliform Organisms on Broiler Growth

DESPITE the general acceptance that antibiotics in broiler feeds evoke growth promoting effects by their action on the intestinal microflora, it must be reemphasized that the mechanism(s) of action is extremely complex. To illustrate this point are the many published reports attesting to divers modes of action. Although it is not the purpose of this paper to present a review of the antibiotic literature relevant to broiler growth, a brief summary will serve to provide a background for elaborating the complex physiology of antibiotics. In a study conducted with ducks, Branion et al. (1953) reviewed many of the mechanisms of antibiotic action and discussed inconsistencies. These inconsistencies have been acknowledged also in reviews by Jukes and Williams (1953), Stokstad (1954) and more recently Klussendorf (1956). Included among the conflicting reports are descriptions of effects from oral and parenteral administration of antibiotics in which some workers have shown that the injected …