LYZ and infection: The serum lysozyme activity was maximum on the 10th day after infection in all fish including the control and the values were found to be 7.58 ± 0.29, 8.33 ± 0.21, 8.90 ± 0.13, 10.76 ± 0.35, 13.88 ± 0.19 and 15.61 ± 0.30 μg/ml for the fish consumed 0, 5, 10, 20, 25 and 50 g leaf extract of Euphorbia hirta respectively.