RESUMO
36 New Zeal and growing male rabbits were used to trace the effects of high dietary levels of monensin on their growth performance, blood picture, internal organs and slaughter value. The used rabbits were randomly allocated into 4 equal groups. Group 1 [control was fed on a balanced basal diet, while groups, 2, 3 and 4 were fed on the same basal diet supplemented with 50, 100, 200 ppm monensin. Dietary monensin adversely affected the final body weight and weight gains of rabbits and the effect was proportional to the dietary monensin level. Proportional to dietary monensin level, the feed intake was markedly reduced. Feed conversion of rabbits was seriously affected and averaged 5.97, 7.01, 9.75 and 10.21 in the respective groups 1-4. The groups receiving diets containing monensin had markedly low dressed carcass weight, dressing% and the weights of head, liver and kidneys. Hematological examination revealed a gradual decrease in RBCs count, Hb and PCV with increasing the level of monensin. Leukocytosis was observed in the group receiving 50 ppm monensin, while a leukopenia was noticed at higher levels. The heterophils decreased significantly, while the lymphocytes were increased. Histopathological examination showed lymphocytic infiltration in the portal areas, irregular necrotic foci in the renal cortex and perivascular lymphocytic cuffing in the cerebral cortex in all monensin treated groups. Hyalinization of the skeletal muscles and brain lesions were observed. The group treated with 200 ppm monensin showed necrosis in the skeletal muscles and focal hyalinization of the cardiac myofibers