Physiological Basis of the Nutritional Value of a Concentrate of Hermetia illucens Larvae in Fish Diets

This article discusses work on assessing the digestibility of a concentrate of Hermetia illucens larvae in fish with gastrointestinal digestion (rainbow trout Oncorhynchus mykiss, Russian sturgeon Acipenser gueldenstaedtii, red tilapia Oreochromis mosambicus × O. niloticus). It was found that this digestibility index of the larvae concentrate was 67–74%. At the same time, fish species consumed larvae protein at 91–97%, the digestibility of residual fat was 90–94%, and easily hydrolyzed carbohydrates amounted to 52–68%. Сhitin of H. illucens was digested 25–35% and did not adversely affect the digestion of protein and fat in the fish species studied. The digestion rates of the H. illucens larvae concentrate, protein, and easily digestible carbohydrates in O. mosambicus × O. niloticus are statistically significantly higher than in Onc. mykiss, while in A. gueldenstaedtii they were intermediate in comparison with tilapia and trout. This corresponded to the duration of food passage through the intestinal tract, which in O. mosambicus × O. niloticus, Ac. gueldenstaedtii, and O. mykiss came to 7.8, 9.6, and 15.7 hours, respectively. Fat and chitin were digested by red trout significantly more efficiently than other fish species. This corresponded to the duration of food passage through the intestinal tract, which for tilapia, sturgeon, and trout came to 7.8, 9.6, and 15.7 hours, respectively. The degree of digestibility of fat and chitin by trout was significantly higher than that of other fish species.