Coccidiosis: Evaluation of anticoccidial drugs in floor-pen trials

Abstract

Methods of obtaining uniform and adequate exposure of chickens to coccidia in floor-pen experiments have been demonstrated in floor-pen trials designed for evaluation of anticoccidial drugs. Use of anticoccidial drugs kept birds susceptible to coccidia up to 4 weeks of age and partially susceptible for 6 weeks. Seeder chickens kept coccidia-free on wire-floored pens until inoculated at a predetermined time with measured doses of sporulated oocysts supplied sufficient exposure to cause mortality and depression of weight gains and feed conversion in withdrawal and nonmedicated controls. Scoring of lesions of a sample of chickens from each pen proved to be the most accurate indicator of coccidial exposure in several trials. The preferred procedure for obtaining exposure was found to be as follows: (a) use a drug to protect against immunity build up; (b) withdraw the drug at 2–3 weeks; (c) add approximately 5% seeder chickens (inoculated with 5× level Coccivac D) directly to the floor of each pen or suspended in cages over the pen; (d) keep litter moist and warm; and (e) lesion score at least 5 chickens per pen 2 weeks after seeder chickens are introduced. All experimental and reference drugs protected the chickens against the litter oocyst exposure, allowing greater body weight gains and better feed conversion than withdrawal or nonmedicated controls.