Fishmeal is consider the main protein source in fish feed, that is why the high demand has affected its production and costs for aquafeeds development, questioning meal supply for the next years. Currently, there is a need to find new alternative inputs to replace fishmeal without affecting the benefits that the latter provides to fish nutrition. Between the most relevant options are black soldier fly larvae (BSFL) and microalgae due to its protein, lipids, vitamins, minerals and antioxidant content; they had been used as partial replacements of fishmeal with favorable results on fish growth performance, however, they had not been used successfully as total fishmeal replacement and neither combined in the same formulation. Therefore, the objective of this study was to develop a balanced fish feed with BSFL and microalgae according to the nutritional requirements of Nile tilapia fry.
Three isoproteic (45%) diets were formulated with 5, 10 y 15% of BSFL and 5% of microalgae Nannochloropsis limnetica; additionally, experimental diets were balanced with animal and vegetal meals as corn, soybean, wheat gluten, wheat bran and meat and bone meal (Table 1). All diets were mixed, pelletized and dried in an oven at 60°C for 24 hours. Feeding trials were conducted for 7 weeks in a recirculation system conformed with tanks of 12 liters, controlled culture conditions of oxygen (5 mg/L), temperature (28°C) and water quality recirculated through an external filter with chemical and mechanical agents. Each tank contained 30 fish of the specie Oreochromis niloticus (1±5 g) and each experimental diet was assigned to triplicate tanks. The experimental diets were compared with a commercial feed.
After 45 days, all experimental diets were well accepted by the fish. Figure 1 shows initial and final weight obtained during the experiment. Fish fed with Diet 3, which contained 15% of BSFL, resulted in a weight increased with significant difference (p<0.05) compared with the other alternative diets. Based on these results, the combination of BSFL at 15% of the diet with 5% of microalgae can be used as a total fishmeal replacement without causing unfavorable effects on fish growth.