Changes in biochemical, histological and specific immune parameters in Catla catla (Ham.) by Cynodon dactylon (L.)

Indian major carp, Catla catla (Ham.), was fed with ethanolic extract of Cynodon dactylon (L.) mixed diet with 0.05% (group A), 0.5% (group B) and 5% (group C) extract for 60 days with an interval of 10 days. Significant (P > 0.05) alterations were observed in the haematological and biochemical parameters such as white blood cell counts, red blood cell counts, haemoglobin content, serum glucose, cholesterol, protein, albumin, globulin, albumin/globulin ratio and RNA/DNA ratio in the experimental diet and control fishes. Non-specific immune response was assessed by the anti-protease activity, which was significantly increased in the experimental diet groups. The specific immune response of fish was evaluated by antibody response against heat-killed Aeromonas hydrophila for 28 days by using ELISA and bacterial agglutination assay. Aggregation of melanomacrophage centres (MMC) and considerable modifications were observed in the histological analysis of the spleen of experimental diet groups. These results suggested that C. dactylon (L.) could combat the microbial infection by stimulating the immune response in fish.