Effect of bacterial single cell protein in rainbow trout (Oncorhynchus mykiss) diet on body composition and digestive enzymes activity

In this study, body composition and digestive enzymes activity was assessed in rainbow trout fry (weight 2.51 ± 0.55 g) fed by bacterial single cell (BSC) as a dietary protein source replaced with fish meal as completely randomized design with triplicate for 6 weeks. Experimental diets were prepared in 5 treatments as isonitrogenous with different levels of fish meal and BSC (100% fish meal (A), 75% fish meal and 25% BSC (B), 50% fish meal and 50% BSC (C), 25% fish meal and 75% BSC (D) and 100% BSC (E)). The body composition findings showed that the highest amount of lipid and protein and the lowest amount of moisture and ash was revealed in fish fed by diet C while the lowest amount of lipid and protein and the highest amount of moisture and ash was observed in fish fed with diet E (P <0.05). Enzymatic assessment from pyloric caeca and intestine were showed that trypsin and α-amylase were increased significantly in fish fed by diet C while alkaline phosphatase activity had the highest amount in diet D than did that from diet E (P <0.05). Based on the results of this study, it is recommended that BSC could be properly replaced up to 50 % with fish meal in rainbow trout fry diet.