Effect of dietary carbohydrate on haematology, respiratory burst activity and histological changes in L. rohita juveniles

A feeding trial was conducted for 60 days to delineate the effect of dietary carbohydrate on the haematology, respiratory burst activity and histology in Labeo rohita juveniles. One hundred and forty four fish (av. wt. 10 ± 0.15 g) were randomly distributed into 12 treatment groups with each of two replicates. Twelve semi-purified diets with either 35% or 28% of crude protein were prepared with different amylase concentrations (0, 50, 100 and 150 mg kg−1) and starch type (gelatinised, G/non-gelatinised, NG) designated as T1 (NG, 35% CP, 0 mg kg−1 amylase), T2 (G, 35% CP, 0 mg kg−1 amylase), T3 (NG, 28% CP, 50 mg kg−1 amylase), T4 (NG, 35% CP, 50 mg kg−1 amylase), T5 (G, 28% CP, 50 mg kg−1 amylase), T6 (G, 35% CP, 50 mg kg−1 amylase), T7 (NG, 28% CP, 100 mg kg−1 amylase), T8 (NG, 35% CP, 100 mg kg−1 amylase), T9 (G, 28% CP, 100 mg kg−1 amylase), T10 (G, 35% CP, 100 mg kg−1 amylase), T11 (NG, 28% CP, 150 mg kg−1 amylase) and T12 (NG, 35% CP, 150 mg kg−1 amylase). The fish were acclimatised to the experimental conditions for 15 days during which time the control diet was fed. The blood haemoglobin percentage and RBC count was not significantly different (P > 0.05) among the various treatments. Highest WBC count, total plasma protein, serum globulin and respiratory burst activity was found at 50 mg kg−1 dietary amylase supplementation, whereas no variation (P > 0.05) was found at 0, 100 and 150 mg kg−1 dietary amylase supplementation. There was no difference (P > 0.05) in the serum albumin and AG ratio among the experimental groups. Feeding either gelatinised or non-gelatinised carbohydrate did not affect the histological structure of the liver, kidney and intestine except in the T4 and T7 groups. The T4 group showed hyperplasia of the intestine and moderate vacuolation in hepatic cells, whereas the T7 group showed hyperplasia of the intestine. Non-gelatinised carbohydrates (46%) along with supplementation with 50 mg kg−1 amylase stimulated the immune system in L. rohita juveniles. But supplementation of amylase to the gelatinised carbohydrate had no immunostimulating effect.