Abstract
This study aimed to assess the immunomodulatory effect of dietary turmeric (TUM) in Oreochromis niloticus juveniles. A total of 240 Oreochromis niloticus fingerlings were divided into four equal groups (n=60), three replicates (n=20) for each: control and TUM-treated groups at 2 (T1), 4 (T2) and 8 (T3) gkg(-1) diets for 8weeks. Body weight gain, leucocytes counts, plasma levels of interleukin 2 (IL-2), interleukin 4 (IL-4), lymphocyte proliferation index to pokeweed mitogen (PWM), nitric oxide (NO) and lysozyme enzyme activities were measured. Histopathology of spleen was performed. TUM at 2gkg(-1) significantly (p<.05) improved weight gain, leucocytes, NO and lysozyme activity than control and other treatment groups. IL-2 level was significantly lower (p<.05) in T2 and T3 than in control and T1, while IL-4 and lymphocyte proliferation index were significantly (p<.05) elevated in T3 than control, T1 and T2. Spleens of T2 showed improvement in white pulp, while spleen of T3 and T4 revealed white pulp depletion. In conclusion, TUM supplementation exerted immunomodulatory effect in Oreochromis niloticus through manipulation of lymphocyte count, IL-2, IL-4 and antibacterial enzymatic activity (NO and lysozyme) that resulted in higher weight gain. Increasing TUM supplementation of fish diets beyond 2gkg(-1) was not beneficial.