Summary
Chickens were selectively bred for either high-antibody (ha) or low-antibody (la) response to sheep erythrocytes. From 6 to 31 days after Streptococcus faecalis challenge exposure, la-line chickens maintained a greater percentage of the prechallenge-exposure body weight and had lower heterophil-to-lymphocyte ratio than did ha-line chickens. The optimal dose of corticosterone (30 mg/kg of feed) was effective in maintaining postchallenge-exposure body weight greater than that of controls. Ampicillin (20 mg/d) alone was ineffective in almost all experiments. Treatment with 30 mg of corticosterone/kg of feed plus ampicillin resulted in increased body weight response to S faecalis infection when treatment was initiated 1 day before or 2 days after challenge exposure. Treatment with corticosterone was more effective in ha- than in la-line chickens. Treatment before challenge exposure was more effective than treatment 2 days after challenge exposure.
