QUANTITATIVE PATHOLOGY OF SMALL-INTESTINAL COCCIDIOSIS CAUSED BY EIMERIA-MAXIMA IN YOUNG BROILERS

The objective of this study was to apply a microscopic lesion scoring system for assessing the severity of experimental coccidiosis. To acco mplish this objective, we examined the effects of varying doses of E. maxima in chicks by comparisons of gross and microscopic lesion scores , body weight gains, feed conversion ratios and faecal oocyst counts. In the battery trial, 3-day-old chicks inoculated with 2.5 X 10(3) or more oocysts had significantly lower growth rate than the controls. Th e mean feed conversion ratio for days 0 to 36 were significantly great er than those of 0 to 10 and 0 to 17 p.i. The intestinal gross lesion scores and microscopic lesion scores were significantly affected by da ys p.i. and oocyst dosage. In the floor pen trials, the mean adjusted body weights of 3- and 14-day-old chicks inoculated with 2.5 X 10(4) o ocysts of the same strain of E. maxima were significantly lower than t he controls. Gross and microscopic lesion scores regressed with signif icant (P<0.05) linearity on body weight gains. Under experimental cond itions, both duodenal and jejunal microscopic lesion scores regressed with significant linearity on gross lesion scores.