Efficacy of Zinc Bacitracin and Sources of Unidentified Growth Factors with Corn-Soybean Meal Type Diet for Turkey Poults

PERHAPS the greatest continuing enigma in poultry nutrition is the variability in growth response to unidentified growth factors and antibiotics. These dietary components are usually considered in separate categories but some evidence shows an inter-relatedness of response. Barnett and Bird (1956) observed that chlortetracycline at 200 p.p.m. greatly reduced the growth response of chicks to fish solubles and pointed out that growth response to antibiotics and unknown factors disappeared at about the same time in the Wisconsin laboratory. Fecal contamination of the diet restored the response to fish solubles and the report of Heth and Bird (1962) indicated that the response to dietary antibiotics was restored at about the same time. Coates et al. (1952) demonstrated that chicks in old but not new quarters responded to antibiotics thereby supporting an “infectivity” aspect to antibiotic responses. The use of antibiotic in the old quarters tended to bring growth rate up to…