The effect of feeding a semipurified diet to chickens infected with coccidia.

Four experiments were conducted using broiler chicks to study the effects of feeding a semipurified diet on coccidial infection. Chickens fed a semipurified diet and inoculated with E. tenella had a very mild infection with little or no mortality and no effect on body weight gain, feed intake, feed conversion ratio, and blood cell loss as judged by hematocrit. At necropsy the infected chickens had light cecal lesions. However, no difference in response was observed between chickens fed either the corn-soybean meal or the semipurified diet and inoculated with a mixture of E. acervulina, E. maxima, and E. brunetti. Chickens fed a diet composed of 25% of the corn-soybean meal diet plus 75% of the semipurified diet and inoculated with E. tenella had the same mortality as chickens fed the corn-soybean meal diet. Feeding chickens the semipurified diet as early as 6 days before inoculation did not affect the severity of E. tenella infection. No difference was observed in the intestinal or cecal pH or food passage time of noninfected chickens fed either the corn-soybean meal or the semipurified diet. No differences were found in the number of oocysts discharged between 2 and 9 hr after inoculation expressed as a percentage of the infective dose. The results of these studies show that a semipurified diet ameliorates infection of chickens with the cecal parasite E. tenella but not coccidial infections of the small intestine.