Effects of different levels of locust meal (Schistocerca gregaria) replacement on growth function, survival, biochemical composition and intestinal digestive enzymes of rainbow trout fingerling (Oncorhynchus mykiss)

The present study was conducted to evaluate of different levels of locust meal (Schistocerca gregaria) on growth function, survival, biochemical composition and intestinal digestive enzymes in rainbow trout fingerling. Four experimental diets with different replacement levels of 0 (control treatment), 15 (SG15), 30 (SG30) and 60% (SG60) of fish meal with locust meal were formulated with equal protein (46.5%) energy (4652 kcal) contents. Diets were distributed in a completely randomized design in four treatment and each with three replications and the average initial weight (5.08±0.33) in 12 tanks for eight weeks (25 pieces of fish in each tank) and Feeding was done three times a day to satiety. Physicochemical parameters such as temperature (17.3°C), dissolved oxygen (6.49 mg), pH (7.55) were constant during the experiment. The results revealed that the highest final weight was observed in 30% treatment (89.34±20.616 %) and differences between 0, 15 and 60% treatments (p<0.05). In 60% treatment, a significant decrease in growth indices and nutritional efficiency was observed (p<0.05). Also, the amounts of protein, fat and moisture in the body of fish were significantly different compared to the control treatment (p>0.05). Analysis of digestive enzymes showed that the highest activity of protease and amylase enzymes was observed in fish fed SG30 diet. The results of this study showed that using 30% locust meal instead of fish meal can improve growth performance, the biochemical composition and digestive enzymes rainbow trout fingerlings.