Feeding de-oiled rice bran based diet with varying level of protein and lipid: Effect on physiological responses of Labeo rohita

A 60- day feeding trial was conducted to study the effects of feeding de-oiled rice bran (DORB) with different dietary protein and lipid levels on the haematological parameters along with digestive, oxidative stress and metabolic enzyme activities of Labeo rohita fingerlings. Nine semi-purified isocaloric (383 Kcal DE/100 g) diets containing varying level of protein (26, 28 & 30%) and lipid (6, 7 & 8%) were formulated as P30L6, P30L7, P30L8, P28L6, P28L7, P28L8, P26L6, P26L7 and P26L8 (P-Protein, L-Lipid), respectively. The fish fed diet with the lowest protein with the highest lipid (P26L8) exhibited significantly (p < 0.05) higher intestinal amylase and lipase activity but no significant variation were observed in total protease activity. The higher HSI (Hepatosomatic index) and ISI (Intestinal somatic index) value along with lower SOD (Superoxide dismutase), CAT (Catalase) and GST (Glutathione-s-transferase) activity of liver and gill were also observed in the same group (p < 0.05). The highest protein and lowest lipid (P30L6) fed group showed significantly (p < 0.05) higher LDH (Lactate dehydrogenase) activity in liver and muscle tissue of Labeo rohita, whereas, there is no significant variation was observed in MDH (Malate dehydrogenase) activity. The haematological parameters like serum protein, albumin, globulin and glucose contents were also significantly (p < 0.05) higher in P26L8 group. RBC (Red blood cell), Hb (Haemoglobin), WBC (White blood cell) and NBT (Nitroblue tetrazolium) value were significantly affected by the dietary lipid level. Fish fed P26L8 treatment group had significantly (P < 0.05) higher AST (Aspartate amino transferase) and ALT (Alanine amino transferase) activity in liver and muscle tissues. Based on the results, it is concluded that feeding de-oiled rice bran with 26% dietary protein and 7% or 8% lipid to L. rohita have no adverse effect on haematological and serum biochemical parameters.