Physio-metabolic and haematological changes of Labeo rohita fed with graded level of de-oiled rice bran-based diet

A 60-day feeding trial was conducted with six experimental diets containing 260 g/kg crude protein and 70 g/kg lipid with varying level of de-oiled rice bran (DORB), viz., 33 (T33), 38 (T38), 43 (T43), 48 (T48), 53 (T53) and 58% (T58) to assess the digestive, metabolic and haematological responses in Labeo rohita. One hundred and eighty (180) fingerlings with ten fish per tank having an average weight of 9.8 +/- 0.5 g were randomly distributed within six treatments in triplicates following a completely randomised design. The amylase and lipase activities in the whole intestine did not vary significantly (P > 0.05), but protease activity varied significantly with respect to DORB level in the diet. At higher (53 and 58%) inclusion level of DORB, the protease activities were lower. T33, T38 and T43 groups showed significantly (P < 0.05) higher aspartate aminotransferase (AST) activity compared to the other groups, whereas lowest activity was recorded in the group fed with highest inclusion level (58%). The oxidative stress enzyme like superoxide dismutase (SOD), catalase and glutathione-S-transferase exhibited significantly higher activities in liver of T58 group of L. rohita. However, the activity of catalase and SOD showed no significant variation in gill tissue. The haematological parameter values such as red blood cell (RBC), white blood cell (WBC), haemoglobin (Hb) and packed cell volume (PCV) were lower in the highest DORB fed group (T58) as compared to their lower DORB inclusion counterparts. No change in NBT value was recorded irrespective of DORB inclusion level in the diet. Hence, from these results, it can be concluded that the dietary inclusion of DORB up to 43% in the diet of L. rohita at 26% crude protein and 7% lipid level is best for the optimal activity of digestive, metabolic and haematological parameters.