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Nicarbazin has recently been described by Cuckler, Malanga, Basso and O'Neill
MATERIALS AND METHODSThe chicks used in these studies were obtained from commercial hatcheries when 1 day old. New Hampshires and Tri-way white crosses of both sexes were used for experiments when 3 weeks of age. In all experiments, the groups were initially balanced for number (10 per group), weight and sex. The chicks were kept in metal, wire-floored, battery brooders in isolation quarters. The water and feed were provided ad libitum; an open-formula laboratory ration, described by Cuckler and Ott (1955), composed of natural feed-stuffs and supplemented with all known required vitamins, was employed. Nicarbazin (0.0125%) was thoroughly mixed into the ration just prior to use.
The strains of coccidia used were pure populations of Eimeria tenella and Eimeria acervulina isolated in our laboratory and Eimeria necatrix, kindly furnished by Dr. E. M. Dickinson, Oregon State College. The procedures used for preparing the homogenates and counting the oocysts were previously described by Cuckler and Malanga (1955).In the immunity studies from 360 to 430 chicks were used in each experiment. Approximately one-half of the chickens were fed the basal ration throughout the experiment. The others were fed nicarbazin-medicated ration beginning 1 day prior to inoculation with oocysts and continuing until the 15th day of the experiment. The nicarbazin-medicated feed was then withdrawn and basal ration was fed for the balance of the experimental period. The oocyst suspensions were inoculated directly into the crop with a syringe. Either a single inoculation or 5 daily inoculations of graded numbers of oocysts were used. In the case of E. tenella, the primary infections were produced with either a single inoculation of 50,000 oocysts or 5 inoculations each of 2,000 or 10,000 oocysts. The infections with E. necatrix were produced with the same numbers as for E. tenella, and in addition a group received 5 inoculations of 400 oocysts. The coccidial exposures used for E. acervulina consisted of either a single inoculation of 500,000 oocysts or 5 inoculations each of 4000, 20,000 or 100,000 oocysts.On the 5th and 9th days after the initial infections, 10 chicks (20 for E. tenella)...
