Fawole, F.J., Sahu, N. P., Pal, A. K. & Arunkumar, R.2024-04-172024-04-172016-1253https://uilspace.unilorin.edu.ng/handle/123456789/11893Aquaculture is an important economic activitysupplying high quality animal protein to greaternumber of people worldwide, and the globalgrowth of the industry remains relatively strongwith an average annual growth rate of 8.6% (FAO2014). However, modern farming techniques andrecent trend of intensification of aquaculture oper-ation has brought in new challenges that threatenthe health of farmed species, leading to growthreduction and immunosuppression, all culminatinginto massive financial loss and reduced profit mar-gins for farmers (Smith, Brown & Hauton 2003;Jha, Pal, Sahu & Mukherjee 2007). Several patho-genic organisms such as bacteria, fungi andviruses have been reported to be principal limitingfactors to the growth of aquaculture industry. Themost common and frequently encountered bacte-rial pathogen in tropical climates isA. hydrophila,which causes severe damage to carp production(Karunasagar, Rosalind & Karunasagar 1991).A 35 days feeding trial was conducted to assess the haemato-immunological response ofLabeo rohita fingerlings fed ethanolic leaf extracts ofPsidiumguajavaandMangifera indica, and infected withAeromonas hydrophila. Six iso-nitrogenous(354.6–361.6 g kg 1) purified diets were preparedwith graded level of leaf extracts viz., control(basal feed without any extract); TG-5 (5 g kg 1guava extract); TG-10 (10 g kg 1guava extract);TM-5 (5 g kg 1mango extract); TM-10(10 g kg 1mango extract); and TGM (5 g kg 1guava extract+5gkg 1mango extract). Haema-tological, immunological, biochemical, along withantioxidant enzyme activities were examined aftera 35 day-feeding trial and following a 7 day chal-lenge withA. hydrophila. The haemoglobin, totalleucocyte and erythrocyte counts, respiratory burstactivity, lysozyme, total protein, albumin and glob-ulin contents increased significantly (P<0.05) inleaf extracts fed groups compared with the controlin pre- and post-challenge conditions. A significant(P<0.05) decrease was observed in SOD (super-oxide dismutase) and catalase activities of thetreatment groups compared with the higher valuein control. The trends in mortality indicated thatgroups of fish showing significantly elevated hae-mato-immunological responses had the lowestmortality following challenge withA. hydrophila.The results showed that extracts ofP. guajavaandM. indicaappear to be potential immunostimulantat an inclusion level of 5 g kg 1in the diet ofrohu. But, mixing of both the extract at similarlevel did not show any synergistic effect, whichneeds to be tested at its lower level of inclusion.leaf extractsguavamangoLabeorohitanon-specific immunitysurvival