Results of replacing fish meal with insect protein in carp feeds

Purpose. Substantiation of the prospects for replacing fish meal in the composition of carp feeds with black soldier fly meal (Hermetia illucens) based on the analysis of studies of productive and individual functional parameters of the body of experimental groups of fish. Methodology. The first stage of the study lasted 30 days and was conducted in laboratory conditions at the Institute of Fisheries of the NAAS: a control and three experimental groups of age-1+ carp were formed, which were reared under identical optimal conditions. The control group of fish received a basic diet; in Experiment 1 black soldier fly meal was added to the feed to replace 100% of soybean meal, in Experiment 2 – to replace 100% of fish meal, in Experiment 3 – to replace 50% of fish meal. The second stage lasted 20 days and was conducted at the Lviv Experimental Station of the Institute of Fisheries of the NAAS in net cages placed in ponds. The control group of age-1+ carp was fed feed without supplements, while the experimental group was fed with black soldier fly meal to replace 100% of fish meal. During the study, the state of the main physicochemical parameters of the rearing environment was monitored. The results were analyzed using methods generally accepted in fish farming. The productive, morphological, hematological and antioxidant parameters of the fish body of experimental and control groups were determined. Findings. During both stages of the study, the temperature, oxygen, and hydrochemical conditions did not differ significantly between the experimental and control variants and met fish farming standards. Laboratory studies of fish sizes and weights showed the highest results compared to the Control were obtained in Experiment 3: body length to height ratio (l/H) – 2.64, body length to girth ratio (l/G) – 1.20, relative weight gain (RWG) – 18.5% against 16.1% in Control. In the carp muscles of all experimental groups, SOD activity was lower compared to the Control with a significant decrease of 49% in Experiments 1 and 2 (p < 0.001), in the hepatopancreas the difference was insignificant. Catalase activity in the hepatopancreas was higher in all experimental groups relative to the control group with the highest value in Experiment 2 (p < 0.01). Reverse trends were found for the content of LPO products (diene conjugates and TBC products) in muscles and hepatopancreas. In general, no significant changes in the activity of the antioxidant protection system were found in the investigated tissues; however, the obtained patterns require additional study for an objective assessment. Studies in cages showed that after complete replacement of fish meal with black lionfish meal in carp feeding, the weight of fish caught was 6.9% lower than in the Control. At the same time, a tendency for an increase in hemoglobin content and the count of erythrocytes in the blood of the experimental group compared to the control group was recorded. Originality.For the first time, the effectiveness of full or partial replacement of fish meal in carp feeds with black soldier fly meal was investigated according to a comprehensive analysis of productive, individual physiological and biochemical parameters of the fish body in the experimental groups. Practical value. The results of the study will allow determining the effectiveness and evaluating the potential of using insect protein in carp feeding on the example of black soldier fly meal. The application of the knowledge gained in fish farming practice will provide an opportunity to replace traditional feed components with an alternative cheap, affordable and environmentally friendly source of animal protein. Keywords: carp, insect protein, black soldier fly, protein source, alternative to fish meal, growth, physiological and biochemical parameters.