Dietary Asparagus racemosus ethanolic root extract modulates immune-biochemical response, immune gene expression and provides protection against Aeromonas hydrophila in Labeo rohita fingerlings

The aim of this study was to investigate the dietary effects of the medicinal herb Asparagus racemosus on immune-biochemical response, immune-related gene expression and resistance of Labeo rohita fingerlings to Aeromonas hydrophila infection. The acute toxicity study showed that the dietary incorporation of the A. racemosus ethanolic root extract (AREE) at the dose up to 2000 mg kg(-1) had no toxic effect on L. rohita. Three experimental diets were prepared with the inclusion of different concentrations of AREE (T1-50, T2-100 and T3-150 mg of AREE kg(-1) feed). Fingerlings of L. rohita were fed with these diets and various immune-biochemical responses and immune-related gene expression were measured on the 0, 15th, and 30th day of feeding. Dietary inclusion of AREE significantly enhanced the biochemical responses (glucose, total protein, albumin and alkaline phosphatase activity), innate immune responses (superoxide anion, lysozyme and myeloperoxidase activity), and mRNA expression of immune-related genes (IL-1 beta, IFN-gamma and C3) in the majority cases. The survivability of rohu against A. hydrophila infection was significantly higher in fish fed with the T2 diet. In conclusion, the dietary A. racemosus ethanolic root extract showed promising immunostimulatory activity, and conferred resistance against A. hydrophila challenge in L. rohita. The dietary supplementation of the extract at the rate of 100 mg kg(-1) feed for 15 days is suggested for obtaining optimal immunostimulatory effect.