The rapidly growing aquaculture industry is dependent on efficient and sustainable aquaculture feeds. Furthermore, commercial aquaculture diets are more expensive compared to other animal feeds. Partly or complete substitute of expensive protein sources with cheap byproducts feed ingredients can drop diet costs and alleviate the environmental impact. Moreover, increasing competition for feed ingredients like soya, wheat, corn, and barley between aquaculture, poultry, and cattle industry and biofuel may threaten aquafeed production’s sustainability . Frass is the waste product from growing black soldier fly larvae after harvesting the larvae. Recently, insect larvae meal has received significant attention as a novel alternative protein source in aquafeed. This byproduct ingredient contains around 200 g/kg protein and significant essential nutrients and normally made of biomass fed into the insect, dead larvae, and larvae excretion. Previous studies suggested that frass addition has a positive impact on vegetable growth and therefore suggested to be applied as a functional biofertilizer. Frass also contains chitin and beneficial microbes, which might have a positive influence on fish intestinal tract health. Recently published data on adding frass in catfish and tilapia diets showed that dietary frass can improve fish performance and the fish immune system.
This study evaluates the potential of dietary Black soldier fly frass on Florida pompano’s growth, body composition, and the intestinal microbiome. Four experimental diets were formulated containing different levels of frass (0, 6, 12, and 18%). The frass was used to replace an equal mixture of corn, wheat, and soybean meal. Juvenile Florida pompano (initial weight of 31.4±0.7 g) were fed to 3% of biomass twice a day for eight weeks. Replacing carbohydrates sources with frass did not improve growth performance resulting in a lower specific growth rate (SGR) and higher feed conversion rate (FCR) (p <?0.05). Frass significantly increased visceral somatic index (VSI) compared to the control diet (4.1-4.6 versus 3.9%). However, the hepatic somatic index (HIS) was lower in fish that were fed with frass-containing diets (0.84-0.92 versus 1.28%) (p <?0.05). Adding frass to the diet did not change the body composition (p?<?0.05).