The study was conducted to evaluate the effect of medicinal plant extracts (Psidium guajava, Eclipta alba, Moringa oleifera) on modulating growth performances, immune responses as well as disease resistance in snakehead fish (Channa striata) against Aeromonas schubertii. The experiment was randomly designed with 10 treatments including 0% (control treatment), 0.01%, 0.1% and 1% P.guajava; 0.01%, 0.1% and 1% E. alba; 0.01%, 0.1% and 1% M. oleifera during 4 weeks and triplicate for each treatment. Fish blood was collected after 2 and 4 weeks (W2, W4) of plant extracts supplementation for hematological analysis, lysozyme, complement activities and total Ig. At the end of experiment, fish were challenged with A. schubertii to evaluate the therapeutic efficacy of medicinal plant extracts. The result showed that the hematological parameters were significantly enhanced following supplemented plant extract diets in dose dependent manners. Specifically, 1% P. guajava, 0.1 and 1% E. prostrata and M. oleifera could statistically increased the total red blood cells (RBC) and white blood cells (WBC) compared to control. The number of lymphocytes were considerably increased in fish fed 1% E. prostrata, 1% M. oleifera. Most of plant extract treatments started to significantly enhance the neutrophil and monocytes compared to control from W2. In addition, the lysozyme activity, complement activity and total of Ig were significantly enhanced in fish fed diets supplemented with 0.1, 1% P. guajava and 1% M. oleifera in W2 and W4. Moreover, supplemented plant extracts diets could improve the mortality in snakehead fish against A. schubertii infection. Especially, treatment supplemented with 1% P. guajava, 1% E. prostrata, 0.1 and 1% M. oleifera significantly reduced the mortality in snakehead fish after challenged with A. schubertii. These results suggested that plant extract diets could play a positive effect in immune response as well as disease resistance in snakehead fish against bacterial infection.
Key words: diseases resistance, immune response, plant extract, snakehead fish,