A feeding trial accounting the whole seawater phase was conducted in commercial sized sea-cages using either a standard commercial feed (Control) or the same feed supplemented with black soldier larvae meal (BSFLM) as a replacement for 4% soy protein concentrate. Each feed was fed to triplicate sea-cages. No adverse welfare issues were observed when the fish were harvested at an average body weight of 4.5kg . The fish fed BSFLM had higher fillet yield and less visceral fat. Raw fillets of salmon fed the BSFLM diet had firmer fillets with less gaping, coinciding with increased level of cysteine and glycine of the connective tissue. Sensory evaluation of baked fillets likewise revealed improved firmness of the salmon fed the BSFLM diet, in addition to higher scores for juiciness, odor, taste and general acceptance.
Atlantic salmon (Salmo salar L.) were farmed in seawater cages on the Norwegian West Coast and fed either a commercial feed ( 36.5% protein and 33% fat) or the same feed where 4% SPC was replaced by black soldier fly (Hermetia illucens) larvae meal . Each diet was fed in triplicate during the seawater phase. At harvesting, fish were scored for external welfare indicators before they were filleted and analyzed for firmness (TA-AX2, SMS) and fillet gaping (score 0-5). Fillets were prepared for sensory testing by baking fillets at 175°C for 12 min (50 participants, hedonic analyses). Skeletal muscle (NQC ) was analyzed for content of fat and astaxanthin. Connective tissue (CT) was isolated from the muscle and analyzed for amino acid (AA ) composition and by Differential Scanning Calorimetry (physical , chemical methods are described in Mørkøre et al. 2020).
Salmon fed BSFLM had higher slaughter yield ( 90.6 vs. 88.3%) and higher fillet yield (61.6 vs. 61%), but fillet fat and pigment content were similar for the fish groups. However , AA composition of the CT showed higher content of cysteine (5.2 vs. 4.4, P=0.05 ) and glycine (296.3 vs. 276.3, P=0.03) ( residues/1000 AA residues), both of which are associated with collagen strength. Results from DSC analyses indicated higher thermal stability of the salmon fed BSFLM compared with the Control (P=0.07). Fish fed the BSFLM achieved higher (positive) scores for odor , taste, juiciness, and firmness as well as general acceptance (Figure 1).