ERP140812 PRJEB55867 57139edf-702f-4ca2-9516-a8ef55ae9506 Potential of shrimp waste meal and insect exuviae as sustainable sources of chitin for fish feeds Chitin is a natural polysaccharide abundantly present in pupal exuviae of some insects, as well as in crustacean shells, and fungi cell membranes. Studies have shown that dietary chitin or its derivate chitosan increases growth rate and feed efficiency of fish. More interesting, chitin acts as a prebiotic by modulating gut microbial communities of fish. Accordingly, the present study aimed to evaluate the impact of two waste by-products rich in chitin, i.e. shrimp meal and insect exuviae (Hermetia illucens) pupal stage, on gut microbiome of rainbow trout (Oncorhynchus mykiss). Three isoproteic, isolipidic, and isoenergetic diets containing either FM, shrimp meal, or FM and 1.6% of pupal exuviae meal were tested. At the end of the feeding trial, no significant differences in fish growth and feed efficiency were observed. In contrast, a modulatory effect of dietary pupal exuviae on gut microbiota was detected. Effect of chitin on trout gut microbiota Chitin is a natural polysaccharide abundantly present in pupal exuviae of some insects, as well as in crustacean shells, and fungi cell membranes. Studies have shown that dietary chitin or its derivate chitosan increases growth rate and feed efficiency of fish. More interesting, chitin acts as a prebiotic by modulating gut microbial communities of fish. Accordingly, the present study aimed to evaluate the impact of two waste by-products rich in chitin, i.e. shrimp meal and insect exuviae (Hermetia illucens) pupal stage, on gut microbiome of rainbow trout (Oncorhynchus mykiss). Three isoproteic, isolipidic, and isoenergetic diets containing either FM, shrimp meal, or FM and 1.6% of pupal exuviae meal were tested. At the end of the feeding trial, no significant differences in fish growth and feed efficiency were observed. In contrast, a modulatory effect of dietary pupal exuviae on gut microbiota was detected. ENA-FIRST-PUBLIC 2023-01-31 ENA-LAST-UPDATE 2023-01-31