Amphora Coffeaeformis Diatom Involved in Reducing the Susceptibility of Nile Tilapia ( Oreochromis Niloticus ) Fingerlings to Aeromonas Hydrophila Infection by Boosting Immune and Antioxidant Responses and Improving Growth Performance Indicators

In the present study, the Amphora coffeaeformis diatom was applied in different concentrations to the diet of Nile tilapia (Oreochromis niloticus) to investigate its potential effects in improving growth performance, as well as enhancing immune and antioxidant responses to control Aeromonas hydrophila infection. The tilapia fingerlings were divided into 4 groups, and for 4 weeks were fed A. coffeaeformis at various concentrations (0, 1, 2 and 3%). Growth-stimulating activity from dietary A. coffeaeformis was observed, particularly in the 2% and 3% treatment groups. Furthermore, serum immunoglobulin M (IgM), nitric oxide (NO), malondialdehyde (MDA), total-superoxide dismutase (T-SOD), catalase (CAT), and glutathione peroxidase (GPx) were evaluated at the 2(nd) and 4(th) weeks from the onset of feeding and showed significant improvement (p < 0.05) in the 2 and 3% groups. At the end of the feeding trial, the tilapia were challenged via an intraperitoneal (IP) injection of virulent Aeromonas hydrophila. Fish survival, serum IgM, nitric oxide, MDA, T-SOD, CAT, GPx, and liver, kidney, spleen, and gill histopathology were all evaluated post challenge. Significant improvements in both immunological and antioxidant parameters continued until the post-challenge measurements. Overall survival was significantly increased in the 2 and 3% groups, compared to the control and 1% groups. Histopathological examination revealed a decrease in the degenerative and destructive effects of A. hydrophila infection on the liver, kidneys, spleen, and gill tissues, indicating that dietary A. coffeaeformis administered at concentrations of 2 and 3% could be recommended as a feed additive for the control of A. hydrophila infection in Nile tilapia.