Feeding de-oiled rice bran (DORB) to Rohu, Labeo rohita: Effect of varying dietary protein and lipid level on growth, body composition, and insulin like growth factor (IGF) expression

Abstract

A 60-day feeding trial was conducted to optimize the dietary protein (30, 28 & 26%) and lipid (6,7 & 8%) levels for optimum inclusion of 33% de-oiled rice bran based (DORB) diets on the growth performance, feed utilization, expression of insulin like growth factor (IGF-I and IGF-II) and RNA/DNA ratio in the Labeo rohita. The formulated diets were different combination of protein and lipid levels while fixing the level of DORB at 33% viz., P30L6, P30L7, P30L8, P28L6, P28L7, P28L8, P26L6, P26L7 and P26L8 (P-Protein, L-Lipid), respectively.Two hundred seventy fingerlings (average wt. 5.56 g ± 0.2) were equally distributed in nine treatments in triplicates with 10 fish per tank. The weight gain % (WG) and specific growth rate (SGR) increased with the decreasing protein level and increasing lipid level in diets. Highest weight gain % and specific growth rate was along with lowest FCR were recorded in the group fed with 26% protein and 7% lipid. The protein efficiency ratio (PER) was significantly (p < 0.05) higher in P26L7 and P26L8 groups. The expression of IGF-I mRNA was found to be higher in P26L7 group as compared to other groups. Though the expression of IGF-II was significantly (p < 0.05) higher in P26L7 group, it was similar to the P26L8 group. The RNA concentration and RNA/DNA ratio was found significantly (p < 0.05) higher in the P26L7 group. Dietary protein level did not affect significantly (p > 0.05) on whole body protein and lipid content. Significantly (p < 0.05) higher body lipid level and lower protein level was found at 26% protein and 8% dietary lipid fed group. Hence, diet containing 33% DORB with 26% crude protein and 7% lipid level is optimal for supporting maximum growth and feed utilization of Labeo rohita.