Eimeria acervulina Infection in the Chicken: A Model System for Estimating Nutrient Requirements During Coccidiosis

Eimeria maxima inoculations of 5 X 10(4) oocysts and E. acervulina inoculations of 2 X 10(5) to 4 X 10(5) oocysts were shown to depress growth by 15 to 20% in young chicks fed crystalline amino acid (CAA) diets. The intestinal lesions produced were typical of light to moderate coccidiosis. In one experiment, the performance of chicks fed monensin was increased in the presence, but not in the absence, of E. acervulina. Thus, monensin prevented the negative effects of E. acervulina on chick performance. This coccidiosis X monensin interaction was also indicative of an active coccidiosis infection. Severe E. acervulina infections were produced by inoculations of 1 X 10(6) or 2 X 10(6) oocysts. Under these conditions, gain was depressed by 30 to 40% and the intestinal lesions produced were indicative of severe coccidiosis. Also, E. acervulina infections were more severe in birds fed CAA diets than in birds fed corn-soybean meal diets. Trypsin incubation of the oocysts prior to inoculation had no significant effect on performance regardless of diet type. Based upon growth rate, intestinal lesions, and responses to anticoccidial drugs, it was clearly demonstrated that coccidiosis of varying severity cn be produced in birds fed CAA diets. In addition, it was observed that the CAA diet, with 24.58% amino acids, contained adequate levels of all indispensable nutrients, even during coccidiosis. This assures that the diet can be used effectively for nutrient requirement studies during coccidiosis.