An experiment was conducted with 48 crossbred rabbits (49 days old) averaging 757.5 ± 0.50 g to assess haematological and serum biochemical response of growing rabbits exposed to varied levels of dietary fumonisin of 0.1, 5.0, 7.5 and 10 mg fumonisin B₁/kg diet containing in diets 1 (control) 2, 3 and 4 respectively, for a period of 12 weeks. Blood samples were collected from the animals through the ear vein, after the feeding trial, for haematological studies and serum biochemistry. Results showed that packed cell volume, haemoglobin concentration and erythrocytes of rabbits fed diets containing 7.5 and 10.0 mg fumonisin B₁/kg were significantly (P < 0.05) lower than those on diets 1 and 2. The white blood cells (WBC) of rabbits fed diet 2 and the control were similar to each other but both were significantly (P < 0.05) lower than those fed diets 3 and 4. Among the leukocyte differential counts examined, neutrophils, eosinophils and monocytes were not significantly (P > 0.05) different among dietary treatments. However, lymphocytes of animals fed control diet were significantly (P < 0.05) lowest (47.83%) as compared to 57.67, 60.00 and 60.50 of animals fed diets 2, 3 and 4, respectively. Platelets and blood constants (MCV, MCH and MCHC) were not significantly (P > 0.05) different among the diets. Serum total protein, albumin and albumin-globulin ratio significantly (P < 0.05) decreased with increase in the dietary fumonisin levels. Serum total protein of rabbits fed diets 3 (5.20 g/dl) and 4 (5.03 g/dl) were identical but both were significantly (P < 0.05) lower than those fed diets 2 (5.60 g/dl) and the control (6.20 g/dl). Urea decreased while creatinine increased apparently with increase in the dietary fumonisin levels. Among the serum enzyme activities examined, AST and ALP were significantly (P < 0.05) elevated in the serum of animals fed diets 3 and 4 than those fed diets 2 and the control. ALT, AST and ALP were significantly (P < 0.05) highest (94.33, 70.00 and 17.37 i.u/l respectively) in animals fed diet 4 containing 10 mg fumonisin B₁/Kg. These results suggest that fumonisin B₁ above 5.0 mg kg^-1 in the diet of growing rabbits significantly altered haematological parameters and induced anaemic condition in the animals. It also depressed serum total protein and enhanced abnormal increase in serum enzyme activities, which is an indication of organ toxicity by cellular destruction induced by the toxin most especially when fed at 7.5 and 10.0 mg fumonisin B₁/Kg diet.

Key words: Rabbits, haematology, serum biochemistry, dietary fumonisin B₁.