The walking catfish (Clarias batrachus) can be easily cultured in warm climates and is inexpensive food at local grocers. In intensive aquaculture, outbreak of disease causes huge economic loss. Antibiotics, vaccines, and various immunostimulants are used to protect fish from pathogens. The applications of antibiotics and chemicals may have a negative impact on consumers. The use of medicinal plant Achyranthes aspera as an immunostimulant is an eco-friendly, sustainable and cost-effective approach to boost up fish immunity. A. aspera is commonly found as a weed in India. The study was carried out to evaluate the effects of A. aspera seeds-and leaves-enriched diets on the performance of Clarias batrachus reared in pond conditions and challenged with Aeromonas hydrophila.
An 85-day feeding trial was conducted in hapas (2.0 m × 1.5 m × 1.5 m) set inside the pond of ICAR-Central Institute of Fisheries Education, Rohtak Centre, Haryana, India. Fish (0.51 ± 0.032 g) were fed with 0.5% seeds (D1), 0.5% leaves (D2) and control diet (D3) without plant ingredients. After feeding, all fish (except sham control) were challenged intraperitoneally with 200 µl of virulent Aeromonas hydrophila (5 × 106 cells/ml). In sham control, fish were challenged with 200 µl of PBS (pH 7.4). Three replicates were used for each feeding regime.
After challenge test, mortality was recorded for 7 days and then blood and tissue samples were collected for various biochemical estimations. The average weight and specific growth rate were significantly (P < 0.05) higher in fish fed with D1 diet followed by D2 and D3 diets. The feed conversion ratio and cumulative mortality rate were significantly (P < 0.05) lower in fish fed with D1 diet followed by D2 and D3 diets. Serum lysozyme, myeloperoxidase, nitric oxide synthase and hemagglutination titer levels were significantly (P < 0.05) higher and thiobarbituric acid reactive substances and carbonyl protein levels were significantly (P < 0.05) lower in D1 diet followed by D2 and D3 diets. The genes iNOS, SOD-C, NF-kB, Bcl-2, BAX, Cytochrome-c, Caspase 9 and Caspase 3 were up-regulated in liver and head kidney of fish fed with experimental diets compared to the control one.
It is evident that A. aspera seeds-and leaves- enriched diets enhance the innate immunity of fish and also play an important role in apoptosis.