Type of black soldier fly (Hermetia illucens) larvae frass influences the nutritional value when included in a prepared diet for Mozambique tilapia (Oreochromis mossambicus)

Abstract

Black soldier fly (Hermetia illucens) larvae (BSFL) farming is expected to increase, and a by-product is the ‘frass’. The dietary inclusion of BSFL frass has been shown to enhance tilapia and catfish growth/immunity. However, the composition of BSFL frass, and potentially their nutritive value to fish, may depend on the initial provided substrate. In this 8-week nutrition trial, BSFL frass made from either expired fish diet (EFD; 45% crude protein) or a combination of fruits/vegetable peels (FV; 9.3% crude protein) were included in the diets of Mozambique tilapia (Oreochromis mozambicus) at 5% or 10%. The EFD and FV frass had a different nitrogen, mineral, and amino acid profile, and this information was used to formulate the diets. Results showed that EFD frass at 10% significantly (P < 0.05) enhanced tilapia growth compared to fish fed the control diet, but performance of fish fed the other test diets were not different (P > 0.05) from the control. There was no significant difference in the crude protein or lipid content of tilapia, but some differences were observed in the amino acid and fatty acid composition. Among the test minerals, only phosphorus was significantly affected, which was higher in tilapia fed the FV frass diets. Liver histology showed some minor inflammation and blood vessel congestion in tilapia fed the 10% frass diets, while the intestinal histology had a better cumulative score among all the frass diets compared to the control. Results indicate that the initial substrate provided to the BSFL can influence the nutritive value of the frass to fish.