Some Physiological Effects of Coccidiosis Caused by Eimeria maxima in Young Chickens

Three battery trials were conducted to study the effects of Eimeria maxima infection on broiler chickens. Four-week-old chicks were individually inoculated with 50,000 sporulated oocysts of E. maxima. Ten inoculated and 10 uninoculated chicks were examined periodically between the 3rd and 21st days postinoculation. In relation to values obtained from the uninoculated chicks, weight gain and pH of the intestinal contents of inoculated chicks were decreased on the 6th day postinocula- tion, and were minimal 2 days later. An increase in erythrocyte sedimentation rate (ESR) of the in- fected chicks was observed on the 10th day, and a decrease in ESR was observed on the 14th day postinoculation. Packed erythrocyte volume was inversely related to ESR in each instance. The light absorbance of the plasma of chicks having coccidiosis was less than that of the control chicks from the 6th to the 14th day after inoculation, the difference being greatest on the 6th and 8th days. Buffy blood coat values of the infected chicks exceeded those of the control chicks on the 10th, 12th, and 14th days postinoculation. With the exception of weight gains in one trial, all measurements of the in- fected chicks approximated those of the control chicks by the 21st day postinoculation. The most pathogenic of the species causing coccidiosis in chickens are Eimeria tenella, E. necatrix, E. brunetti, and E. maxima (Lund and Farr, 1965). Most of the published reports deal with infections of E. tenella, and rela- tively few have been concerned with E. maxima. Since the results of surveys (Levine, 1940; Zimmerman, 1957; Edgar, 1958; Chute