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.
