Effect of dietary supplementation of cassia auriculata leaf powder on growth and immune responses of milkfish, Chanos chanos

A 30 days feeding trial was conducted to evaluate the effects of Cassia auriculata leaf powder on growth and immunomological parameters of the juveniles of Milkfish, Chanos chanos and disease resistance against Vibrio anguillarum. The juvenile fishes with an average weight of 20±3 g were stocked in four treatments each with three replicates. Four practical diets were prepared with graded level of Cassia auriculata leaf powder (CAL) at the rate of 0%, 0.5%, 1% and 1.5% and fed to four treatments respectively named as CAL0, CAL0.5, CAL1 and CAL1.5. At the end of the experiment blood samples were collected for immunological parameters. After sampling, the remaining fishes were challenged with 0.1 mL of virulent V. anguillarum suspension at a concentration of 107 CFU mL-1 and mortality was observed for 7 days. Post challenge sampling was performed for the collection of blood samples. The growth parameters such as Weight gain%, SGR%, PER were positively affected by Cassia auriculata leaf powder incorporated diet. Higher weight gain %, SGR% and PER were noticed in CAL1.5 group followed by CAL1, CAL0.5 and CAL0. The respiratory burst, lysozyme and phagocytic activities were increased with increasing level of CAL in the diet which indicates better immune response of the fishes fed with CAL. The higher respiratory burst (0.522 ± 0.03), lysozyme (70.07 ± 1.57) and phagocytic (52.91 ± 1.76) activitieswere observed in CAL1.5, CAL1 and CAL1.5 groups respectively during pre-challenge and post challenge. There was significant difference in the survival rate of control (CAL0) and CAL incorporated diet fed groups (P<0.05). Maximum survival was witnessed in CAL1 followed by CAL1.5 and least survival was in CAL0 group. The results indicate that diets supplemented with 1% CAL potentially enhance the immune system and effectively protects the host against V. anguillarum infection and thereby improve the survivability of the fish against this dreadful pathogen.