Growth, Health and Fillet Quality of Rainbow Trout ( <i>Oncorhynchus mykiss</i>) Fed Directly with Black Soldier Fly ( <i>Hermetia illucens</i>) Prepupae

Black soldier fly (BSF; Hermetia illucens) has received growing attention as an alternative sustainable ingredient for aquafeeds. This study aimed to investigate the effects of direct BSF feeding on growth, health, and filet quality of rainbow trout. Fish were fed with dried black soldier fly (BSF) prepupae for one, two, or three meals a day. After 90 days of feeding, a substantial reduction in growth was found in dried BSF fed groups as daily dried BSF meal increased. Rejection and reduction in feed intake were only observed in the fish group that was fed with dried BSF 3 times a day. Amino acid content of BSF prepupae was significantly higher than that of commercial diet and some of the fatty acid contents were similar toor higher than commercial diet. When fish were fed with dried BSF 2 or 3 times a day, chitin accumulated in the fish's gut, causing constipation and leading to a decreased or rejected feed intake. A substantial decreasing trend was detected in arginine, histidine, and threonine with the increase in the number of dried BSF meals, while isoleucine, leucine, tryptophan, and alanine levels were considerably increased. Inclusion of one dried BSF meal in a daily feeding resulted in improvements in fish PUFAn-3, PUFAn-6, and DPA fatty acid levels.