Effects of canola protein hydrolysate (CPH) on growth performance, blood biochemistry, immunity, and gastrointestinal microbiota of beluga (Huso huso) juveniles

This study assessed the effects of diets supplemented with canola protein hydrolysate (CPH) on growth performance, blood biochemistry, immunity, and gastrointestinal microbiota of beluga (Huso huso) juveniles. CPH concentrations of 0, 300, 400, and 500 mg kg^-1 diet were denoted as control, CPH_300, CPH_400, and CPH_500, respectively and were added to fish basal diet. 840 beluga juveniles (30±6 g) were assigned into the four dietary treatments and fed for 56 days. The diet supplemented with 500 mg kg^-1 of CPH significantly decreased food conversion ratio (FCR). Condition factor (CF), specific growth rate (SGR), body weight gain (BWI), standard length (SL), total length (TL), survival rate, and food consumption demonstrated a CPH dose-dependent increase, with highest values in the fish treated with CPH_500. Concentrations of blood (serum) cholesterol, triglyceride, and glucose decreased in a CPH- concentration dependent manner as well. Red blood cells (RBC) and white blood cells (WBC) increased and decreased, respectively in all fish treated with CHP, especially in CPH_500 treatment. Moreover, gastrointestinal population of Lactobacillus spp. and total bacteria were significantly enhanced in the treated groups, with the highest loads of total bacterial (2.1×10^6 CFU) and Lactobacillus spp. (1.6×10^4 CFU) in CPH_500 treatment. Taken together, CPH could be introduced as an alternative for fishmeal in beluga diet, although more studies are needed to be conducted to elucidate the underlying mechanisms by which CPH improves fish growth.