Effects of dietary anthocyanin on innate immune parameters, gene expression responses, and ammonia resistance of Nile tilapia (Oreochromis niloticus)

The present study investigated the effects of dietary anthocyanin on the growth performance, haematological, non-specific immune, and spleen gene expression responses of Nile tilapia, Oreochromis niloticus. Five experimental groups of fish with mean weights of 8.24 +/- 0.64 g were used in the study; four of these were fed with diets incorporating anthocyanin (20 mg kg(-1), 40 mg kg(-1), 80 mg kg(-1) and 160 mg kg(-1)), while the fifth was a control group without dietary anthocyanin. Growth performance and haematological parameters of tilapia were not affected by anthocyanin-supplemented diets (p > 0.05). Dietary anthocyanin significantly increased respiratory burst activity, phagocytic activity, phagocytic index, lysozyme activity, myeloperoxidase activity, serum total superoxide dismutase (T.SOD) activity, and serum catalase (CAT) activity (p < 0.05). The total immunoglobulin level was highest in the 80 mg kg(-1) group compared with the other groups (p < 0.05). In addition, with the anthocyanin-containing diets, the gene levels of interleukin 1, beta (IL-1 beta), interleukin 8 (IL-8), tumor necrosis factor (TNF-alpha), heat shock protein 70 (HSP70), and interferon gamma (IFN-gamma) were increased in the fish spleen, and the gene levels of CAT, GPx, and SOD were also increased in fish liver (p < 0.05). At the end of the experiment, the fish were subjected to ammonia stress. The groups fed with 20 and 40 mg kg(-1) anthocyanin exhibited higher survival rates than the other groups. In summary, feeding Nile tilapia with anthocyanin-containing diets caused increases in the innate immune parameters, gene expression responses, and the survival rate of the fish subjected to ammonia stress.