Protective Effects of Supplemented Diet on Antibacterial Activity and Immune Responses in Rohu Fingerlings, (Hamilton), Subjected to Infection.

The current study focuses on the antibacterial activity and potential efficiency of dietary supplements of on the immune response, improved growth performance, and disease resistance of fingerlings against infection. Crude ethanolic extract of and partially purified fractions of the extract were tested against two selected fish pathogens using the disc diffusion method. A total number of 360 rohu fingerlings (25 ± 2 g) were allocated to 4 treatments for 90 days. They were fed with an experimental diet containing powder (0, 0.1, 0.5, and 1.0 g Kg of a basic diet). To evaluate the non-specific immunity parameters including serum bactericidal, lysozyme activity, superoxide anion production, and biochemical and haematological indices, the fish were sampled at day 30, 60, 90, and after bacterial challenge. Mortalities of the fish were observed over 10 days post challenge with . The protein and globulin levels of the treatment group were significantly higher after being treated with than those of the control group. The total blood-cell count and haemoglobin content were also increased in the algal-diet-treated group. Among all the experimental diets, the 0.5 g Kg fed group of fish showed significantly ( < 0.05) increased serum bactericidal activity and superoxide anion production when compared with the control group on day 90. Maximum lysozyme activity (750.00 ± 3.27) was noticed in the 1.0 g Kg diet fed group on day 30. The treated group exhibited a better growth performance of the fish. The maximum survivability (86.5%) was recorded in the 1.0 g Kg diet fed group at the end of the 10-day fish exposure to . These results suggest that the optimum dietary supplementation could be 0.5-1.0 g Kg of the diet, which stimulates immunity and protects from infection.