Can black soldier fly meal in diets improve gut microbiota diversity, nutrient digestibility, and growth response of marine fish? A study on red sea bream Pagrus major.

The present study assessed the growth and fish performance of juvenile red sea bream fed four isonitrogenous (46–48%) and isolipidic (15%) diets containing 45% fishmeal (control) and 15%, 30%, and 45% defatted black soldier fly (BSF) Hermetia illucens meal for 67 days. Subsequent analyses showed that there were no significant differences in the growth parameters, nutrient digestibility, and body composition of fish among all treatments. Although no significant difference was observed in fish growth, low growth was observed when the fish meal was totally replaced with the BSF meal. Higher alpha diversity of intestinal microbiota was observed in fish fed the BSF meal-based diet compared to that of the control. In the treatment groups fed the BSF meal, elevations in the presence of microbial genera that produce digestive enzymes, such as chitinase (Nocardia, Vibrio, Paenibacillus, Photobacterium), lipase (Paenibacillus, Photobacterium), and trypsin-like serine protease (Bacillus, Paenibacillus) and vitamin B group [biotin (Vibrio, Paenibacillus, Bacillus), cobalamin (Pseudomonas, Bacillus, Propionibacterium), and pyridoxin (Photobacterium)], were observed. We also found an increasing trend of bacteria producing antioxidative enzymes, such as superoxide dismutase and catalase (Nocardia, Pseudomonas, Photobacterium) in the BSF groups. These results suggested that the BSF meal could replace 67% of fishmeal without causing a negative impact on growth and lead to beneficial effects on the intestinal microbiota of the red sea bream. [ABSTRACT FROM AUTHOR]