Biological tests of Hermetia illucens larvae hydrolysate as a composition of compound feed for trout in industrial aquaculture

The problem of animal protein deficiency is relevant in aquaculture feed production. The larvae of the black soldier fly Hermetia illucens are increasingly used, but due to the presence of chitin, they are not fully absorbed. The aim of the study was to assess the rationality of using larval hydrolysate in biological tests for growing rainbow trout fry. In an experiment based on high-temperature hydrolysis of the larvae, a water-soluble additive was obtained in dry form, introduced into compound feed instead of part of the fish meal, and fish indicators were analyzed. The chemical composition of the larva and its hydrolysate was studied. The protein content in the larva and supplement was 17.8% and 43.4%, the chitin in the larva was 7.5%, and it was absent in the hydrolysate. Analysis of the amino acid composition of the proteins of the larva, its water-soluble supplement and fish meal showed that they are close. Biological tests were carried out at the fish-breeding enterprise PROMKORM LTD, for 30 days in RAS installations on 2 batches of trout (experimental and control). In the control experiments, industrial feed recipes for trout were used. In the experiment, 10% of fish meal in the basic feed recipe was replaced by 10% of the larva hydrolysate. The weight, hematological and morphophysiological parameters of fish were studied. At the end of the experiment, the chemical composition of the young fish of both groups was almost identical. No reliable differences were noted when comparing the parameters of length, weight, Fulton fatness coefficient, obesity degree, liver, heart and spleen indices. Blood parameters (the concentration of erythrocytes, lymphocytes, hemoglobin in the blood and in the erythrocyte, protein in the blood serum) were somewhat better in the experimental fish, but the differences were not statistically reliable. Water-soluble hydrolysate of the larva of Hermetia illucens can be considered a promising additive for aquaculture.