Prophylactic Efficacy of Graded Levels of Ipronidazole Against Different Levels of Exposure to Histomoniasis in Turkeys 5 and 12 Weeks Old

Abstract

Two experiments were conducted with Large White turkeys 5 to 9 and 12 to 17 weeks of age. Birds were fed 0.000, 0.00156, 0.00312 or 0.00625 percent of ipronidazole and given different exposures to histomoniasis. The exposures consisted of graded doses of embryonated Heterakis gallinae ova (containing Histomonas meleagridis) administered orally. Histomoniasis mortality was recorded during post-exposure periods of 28 or 35 days; dead birds were examined for hepatic and cecal lesions typical for histomoniasis. Birds which survived the post-exposure period were sacrificed and examined for hepatic and cecal lesions.Mortality and morbidity results varied according to the graded doses of infective material given with either the unmedicated diet or 0.00156 percent of ipronidazole. The 0.00625 percent level of ipronidazole in feed was highly effective in preventing histomoniasis mortality and morbidity in both experiments. Lower levels of drug (0.00156 and 0.00312%) were clearly more effective against histomoniasis in younger (5 to 9 weeks) than in older (12 to 17 weeks) turkeys. Mortality was 25.0 and 4.2 percent, respectively, among the younger turkeys receiving 0.00156 and 0.00312 percent of ipronidazole. The same levels of drug allowed 60.7 and 25.0 percent mortality, respectively, among turkeys 12 to 17 weeks old. It would appear that the level of ipronidazole for prevention of histomoniasis should not be decreased, but should perhaps be increased in the diet of growing-finishing turkeys.