Investigations on the Use of Clopidol Coccidiostat for Replacement Pullets

STOCK et al. (1966) reported clopidol to be an effective, broad spectrum coccidiostat for broiler chickens. Reid and Brewer (1967) and Long and Millard (1967) have confirmed the efficacy of clopidol and have demonstrated that the drug, a true coccidiostat, arrests an early stage of the Eimeria life cycle. The sporozites invade the intestinal tissue, reaching the normal site for development, but further growth is then inhibited (Long and Millard, 1967). Lohlammert (1967) performed histological studies and reported E. tenella development was affected 24 hours post-infection. Reid and Brewer (1967) concluded that coccidiosis outbreaks could occur after withdrawal of clopidol medication since the early endogenous stages of the parasite do not induce immunity in poultry. They therefore considered clopidol to be useful in broilers, but cautioned that clopidol medication might restrict development of immunity in replacement flocks. The purpose of the preliminary battery studies reported herein was to determine if…