IMMUNITY TO EIMERIA IN BROILERS REARED ON NICARBAZIN AND SALINOMYCIN

The incidence of oocysts was monitored in the litter at two broiler farms where birds were reared to 8 wk of age using a shuttle program involving nicarbazin (from 0 to 21 days of age) and salinomycin (from 21 to 44 days of age). Some birds from these farms were challenged with three species of Eimeria to see whether immunity had developed as a result of prior exposure to infection. Oocysts of at least three species of Eimeria were present in small numbers in the litter. Birds from both farms were immune to Eimeria acervulina and Eimeria maxima (judged by weight gain) although the immunity was incomplete as evidence by oocyst production. Birds from one farm were immune to Eimeria tenella (judged by weight gain) but birds from the other farm were susceptible to this species.