IMMUNORESPONSIVENESS OF FAST-GROWING CHICKENS INFLUENCED BY FEEDING REGIMEN

1. Immunoresponsiveness and disease resistance were measured in broile r males maintained on an libitum feeding throughout or on alternate-da y feeding. Alternate-day restrictions were started 1 and 2 d after hat ch so that on any one day there were chicks fed and fasted. 2. Severit y of response to E. coli challenge as measured by lesion scores, and m ortality was greater for chicks fed ad libitum than those fed on alter nate days. For chicks fed on alternate days, lesion scores were lower for those without access to feed for the 24-h period immediately after challenge. 3. Spleen weights, the indicator of response to marble spl een disease virus challenge, were higher for chicks fed ad libitum tha n those fed on alternate days. 4. Antibody response to sheep red blood cell antigen was not affected by feeding regimen. 5. Ratios of hetero phils to lymphocytes were higher for chicks given access to feed for t he previous 24-h period than for those fasted during the previous 24-h or those that had been fed ad libitum. 6. Results of this experiment suggest that for alternate-day feeding programs, vaccination be admini stered on the day that chicks are not fed.