Preliminary assessment of the nutritive value of dietary exuviae from black soldier fly (Hermetia illucens) pupae in Mozambique tilapia

Abstract

A by-product of black soldier fly (Hermetia illucens) larvae (BSFL) farming is the chitin-rich “exuviae” (exoskeleton shell) that is left behind after the prepupae larvae metamorphose into adults. Moreover, exuviae is present in BSFL meal and frass. In this 8-week trial, tilapia (initial weight of 2.93 g) were fed diets with increasing inclusions of dietary BSFL exuviae (0%, 0.05%, 0.1%, or 0.5%) and the growth, biochemical composition, hepatic expression set of genes related to metabolism as well as liver/intestinal histomorphology were examined. Growth metrics tended (p = 0.066) to increase linearly with increasing exuviae level, although the feed conversion ratio was unaffected. Muscle P and Zn content were significantly linear and/or quadratic with respect to dietary exuviae level and were highest in fish fed the control diet and lower in fish fed diets with exuviae. Dietary BSFL exuviae at 0.1% and 0.5% significantly downregulated the hepatic expression of lipoprotein lipase, trypsinogen, and cytochrome P450 1A (cyp1a) genes relative to control. Liver histology and scoring revealed mild to severe changes ranging from localized inflammation to necrosis and hemorrhaging with increasing exuviae content, while intestinal histology appeared similar among treatments. Muscle protein and amino acids decreased either linearly or quadratically with increasing BSFL exuviae. Muscle lipid and fatty acid profiles were not significantly impacted by dietary treatments. Results suggest that dietary inclusion of BSFL exuviae up to 0.5% of diet did not limit tilapia performance, but further research is needed on treatments of BSFL meal or exuviae prior to diet inclusion to reduce liver pathologies and potentially enhance fish production.