Dietary supplementation with açai (Euterpe oleracea) improved the haemato-immunological parameters and growth performance of koi carp (Cyprinus Carpio Linnaeus, 1758).

Amazonian phytotherapeutics show great potential in treating various diseases and have proven effective in aquaculture. Açai, a plant rich in antioxidants, essential fatty acids, and anti-inflammatory properties, is a promising feed additive for fish. This study evaluated the effects of dietary supplementation with açai in the diet of the juvenile koi carp Cyprinus carpio (Koi variety). For this purpose, the fish were subjected to five dietary treatments with different amounts of açai in the feed [0, 5, 10, 15 and 20 g kg^-1] for 60 days. Phytochemical analyses revealed that the contents of phenolic compounds, flavonoids, tannins, and carotenoids and the antioxidant potential of the experimental diets increased as the inclusion volume increased. At the end of the feed trial, the growth performance, haematoimmunological parameters, and chemical analysis of the fillet and skin of the fish were evaluated. Weight gain, daily weight gain, biomass gain, daily biomass gain, and feed conversion were significantly greater (p < 0.05) in the 15 g kg^-1 group than in the 5 g kg^-1 and control groups. In terms of haematology, the number of thrombocytes was significantly greater (p < 0.05) in the fish from the 20 g kg^-1 treatment group than in those from the control group. The plasma antimicrobial activity significantly increased (p < 0.05) in the 15 g kg^-1 and 20 g kg^-1 treatments, whereas the agglutination titre was significantly positive (p < 0.05) in the açai treatments compared with the control group. The results indicated that freeze-dried açai pulp could be used as a growth promoter and improve the innate immune response of C. carpio after 60 days of dietary supplementation.