Modirsanei, M., Khosravi, A.R., Kiaei, S.M.M., Bozorgmehri Fard, M.H., Gharagozloo, M.J. and Khazraeinia, P. 2004. Efficacy of dietary natural zeolite and Saccharomyces cerevisiae in counteracting aflatoxicosis in broiler chicks. J. Appl. Anim. Res., 26: 39–44. Six hundred male day-old broiler chicks were assigned to a completely randomized design arrangement of treatments to evaluate the efficacy of Saccharomyces crervisiae (SC) or a natural zeolite (NZ) at the level of 0.5 and 0.75per cent, respectively, to reduce toxic effects of aflatoxin B1 (AFBB1) at the level of 1.0 mg/kg of diet in broiler chicks in a 35d experiment. Feeding diets containing AFB1 significantly and adversely affected body weight gain, feed intake, feed efficiency, total serum protein, prothrombin tune and weight of thymus but not that of bursa of Fabricius, liver or spleen and caused histopathological changes in liver, bursa of Fabricius and thymus. Addition of 0.75 per cent NZ to diet did not reduce any of the adverse effects, whereas, supplementation of 0.5% SC partially ameliorated these adverse effects in respect of weight gain, feed efficiency, total serum protein and prothrombin time.