Further Evidence on the Relation of Coliforms to the Growth Response of Chicks to Antibiotics

PREVIOUS work has shown that the growth response of chicks to antibiotics is often accompanied by increases in intestinal coliforms (Anderson et al., 1952; and Slinger et al., 1954). Anderson et al. (1953) and Romoser et al. (1953) showed that the feeding of coliform bacteria stimulates the growth of chicks. Aureomycin has been found to spare the requirement of the chick for folic acid (Biely and March, 1951). More recently Rhodes et al. (1954) have reported that the coliform bacteria isolated from the intestinal tracts of antibiotic-fed birds synthesized larger amounts of extracellular folic acid than those from birds fed diets with antibiotics. In an attempt to obtain further information on the relation of coliform bacteria to the growth response of chicks to antibiotics two experiments were made. In the first experiment it was desired to determine the effect of feeding various levels of chloromycetin on the growth and intestinal …