Protection of bacterial infection through dietary administration of Azadirachta indica (neem) leaf in Chinese carp after parasitic infestation

The present study determined the protection afforded by dietary administration with Azadirachta indica extract in terms of mortality and innate immune response to Aeromonas hydrophila infection in silver carp, Hypophthalmichthys molitrix after parasitic infestation in the aquarium. The silver carp was fed with 0% (control), 1.0%, 2.0% and 3.0% supplementation diets at weeks 1, 2, and 4. 2.0% dose diet within all enriched diets showed significantly increased weight gain (WG); 51.3 ± 1.0 g from weeks 1 to 4 while the specific growth rate (SGR), and feed conversion ratio (FCR) did not change significantly when compared to the control. The hematocrit, lymphocytes, and neutrophils significantly increased when fed with 2.0% supplementation diets against pathogen. The phagocytic index, bactericidal activity significantly increased in fish fed with 2.0% dose diet from weeks 1 to 4 as compared to the control, but not with 1.0% and 3.0%. The highest protection by means of lower cumulative mortality was recorded with 2.0% diet when compared to 0%, 1.0% and 3.0% diet. This study suggested that 2.0% supplementation diet significantly influence the growth, hematology, and enhances the innate immune system in silver carp, H. molitrix against A. hydrophila.