Dietary black soldier fly pulp affects growth, antioxidant and immune capacity of Micropterus salmoides

Dried or defatted black soldier fly (Hermetia illucens) larvae meal has been shown an important ingredient in aquafeed, but little information is available about the effects of black soldier fly pulp (BSFP) on growth and health of fish. A 62-day feeding trial was conducted to assess the effects of dietary BSFP on growth performance, whole body composition, serum metabolites, antioxidant and immune response of Micropterus salmoides. Four isoproteic and isolipidic diets were formulated by adding BSFP (original substance) to the basal diet at the rate of 0% (BSFP0), 1% (BSFP1), 2% (BSFP2) and 4% (BSFP4), corresponding to inclusion of 0, 4.5, 9.0 and 18.0 g/kg DM in diets. Each diet was randomly assigned to triplicate groups of 35 fish per tank. Fish were fed twice daily to apparent satiation. Blood samples were collected at the terminal trial to analyse serum metabolites, antioxidant and immune enzyme activities. Results indicated that fish fed BSFP2 had higher (P<0.05) weight gain rate, specific growth rate and intraperitoneal fat ratio than those of fish fed other diets. Crude lipid, ash and calcium contents were higher (P<0.05) in BSFP2 than those in BSFP0. Fish fed BSFP2 and BSFP4 had lower (P<0.05) serum malonaldehyde but higher (P<0.05) acid phosphatase than other diets. It was concluded that dietary inclusion of BSFP improved growth performance of M. salmoides might be attributed to increased lipid and ash deposition. BSFP improved antioxidant and immune capacity but also increased intraperitoneal fat deposition of fish, suggesting BSFP should be careful to be used in M. salmoides diets.