Response of Hormone-Injected New Hampshire Chickens to Antibiotic Supplementation

Previous work at this station has shown that in certain strains of New Hampshire chicks there exists a sex differential in growth response to antibiotic supplementation. Begin et al. (1953) observed that at 10 weeks of age the difference between the growth rate of male chicks fed an all vegetable-protein basal ration and the rate of those fed the basal ration supplemented with bacitracin was highly significant. The females on this same bacitracin supplemented ration and in the same pen failed to respond in a significant manner. Palafox and Rosenberg (1952) found a difference in sex response in New Hampshire chicks fed either a commercial aureomycin or terramycin feeding supplement. In their work the males in most instances exhibited a higher percentage growth response than did female chicks. The trial reported here was designed to study the growth response to bacitracin of birds whose sex had been modified by subcutaneous …