Chitin digestibility and intestinal exochitinase activity in Nile tilapia and rainbow trout fed different black soldier fly larvae meal size fractions

Black soldier fly (Hermetia illucens) larvae meal (BSFLM) is a novel fish feed ingredient with high crude protein content (~40% dry matter, DM). However, BSFLM also contains chitin, which might impair nutrient digestibility. To investigate the effect of chitin on digestibility and chitinase activity in fish, different contents were tested as ingredients for Nile tilapia (Oreochromis niloticus) rainbow trout (Oncorhynchus mykiss). was sieved into three size fractions obtaining contents: 0–200 ?m (fine), 200–400 (medium), >400 (coarse), 1.8, 2.7 15.4% DM basis, respectively. Four isoenergetic isonitrogenous diets formulated each species including an experimental reference diet replacing 25% matrix one fractions. Dietary inclusion coarse fraction resulted significantly lower apparent DM, protein, nitrogen-free extract when compared other treatment groups both species, supports hypothesis that act anti-nutrient. it found could digest but its decreased higher dietary level. Furthermore, ?-N-acetylglucosaminidase (exochitinase) increased proximal distal intestine suggesting exochitinase production can be upregulated depending intake. Overall, results corroborate source well anti-nutrient trout.