Effects of dietary incorporation of Hathawariya leaves (Asparagus racemosus) powder on immune response and resistance to Aeromonas hydrophilla in Koi carp (Cyprinus carpio)

Abstract

Few research studies have been conducted with the aim of developing immune-stimulating feeds for the ornamental fish industry in Sri Lanka. Therefore, the present study was conducted to identify the most effective immuno-stimulant concentration of Hathavariya leaf (Asparagus racemosus) powder as a diet for Koi fish (Cyprinus carpio) against Aeromonas hydrophilla. A total of 120 Koi carp (4.0 - 4.5 g) were fed for 60 days with four treatments (in triplicate) to investigate immune response and growth performance. Fish in four nutritional treatments (T1, T2, T3 and T4-control) were fed diets containing 1%, 2.5%, 5% and 0% A. racemosus leaf powder, respectively. A challenge study using PCR tested A. hydrophilla was done at the end of 60 days and blood sampling was done after a five-day challenge test. Complete randomized design was used as the experimental design and all data were analyzed using one way ANOVA after normality testing. All the tests were carried out using statistical software Mini tab (17). The results revealed no significant (p > 0.05) differences in growth parameters. KOI carp fed the control diet had the highest weight gain and SGR while fish fed the T1 diet had the least. WBC value in T2 was significantly (p < 0.05) higher than other treatments and significantly (p < 0.05) decreased in control diet. In addition, fish fed T2 treatment had the highest percentage values of lymphocytes (72.0 ± 5.6), neutrophils (25.0 ± 11.3) and survival rate (77.8). Therefore, the results of this study revealed that 2.5% A. racemosus powder incorporated T2 diet has a possible immune effect against A. hydrophilla. Further research is essential in the future to identify an active chemical component in Hathavariya leaf that acts against A. hydrophila.