Black Soldier Fly Larvae Meal vs. Soy Protein Concentrate Meal: A Comparative Digestibility Study in Barramundi (Lates calcarifer)

Black soldier fly larvae meal (BSFM) from Hermetia illucens has emerged as a dependable protein source in aquaculture. This study aimed to assess BSFM's digestibility in barramundi juveniles and compare it to soy protein concentrate meal (SPCM). Four diets (control, 30% BSFM; 30% SPCM; and commercial feed control) were tested on 1,800 barramundi juveniles (weight: 71.1 g) over 51 days in a recirculating aquaculture system (RAS). The final body weight (FBW) of fish fed with BSFM reached 222.2 (+/- 8.7), with a thermal-unit growth coefficient (TGC) of 4.33 (+/- 0.15) and a feed conversion ratio (FCR) of 1.04 (+/- 0.01). While BSFM and SPCM inclusion did not significantly impact FBW, body weight gain (BWG), TGC, or survival rates (P > 0.05), FCR increased. BSFM significantly raised total feed intake (P < 0.05) but did not affect daily feed intake (P > 0.05). Importantly, BSFM and SPCM inclusion did not alter diet apparent digestibility coefficient (ADC) for any nutrient groups (P > 0.05), with BSFM showing high ADC for dry matter (76.8%), crude protein (93.2%), and gross energy (83.9%). No significant difference (P > 0.05) was observed in these ADCs between BSFM and SPCM. The high digestibility of BSFM in warm seawater RAS (29.4 degrees C) under high stocking density (33.7 kg m(-3)) supports its efficacy in contemporary barramundi farming.