Trial on Using Some of Herbal Extracts as Promising Immunoprophylaxis Feed Additives in Cultured Oreochromis niloticus

M EDICINAL HERBS and some plant extracts are natural feed additives which have a great impact on fish health. The present study focused on three dietary plant extracts to determine which one could be used as immunostimulant in aqua-feed. A total of 210 apparently healthy O. niloticus with an average body weight 30 g were stocked in 21 glass aquaria (10 fish/group/replicate) (3 replicate/group) and fed on pelleted diet supplemented with (0.5mg, 1mg onion leaves extracts {OE}, 0.5mg. 1mg barely seed extracts{BE}, 0.5mg, 1mg rice straw extracts {RE }and 0% additive) twice daily for two months. The blood picture, innate immunological parameters and response toward pathogens were assessed. At the end of experiment there was significant increase (P 0.05) in serum lysozyme activity, phagocytosis in groups fed OE and BE extracts while there is no effect in fish fed RE extract. Globulin level and WBCS count increased in OE and BE groups. The result of this study demonstrated that fish groups fed on OE exhibited the highest immune performance and resistance against experimental infection with Aeromonas hydrophila, coming in the second rank the BE, and to lesser extent the RE which was nearly similar to control group. Therefore, we can recommend the use of onion leaves extract in aqua-feed at 0.5mg/kg diet andor barley seed extract at 1mg/kg diet.