Effects of dietary Andrographis paniculata extract on growth, haematological, immune responses, immune-related genes expression of ornamental goldfish (Carassius auratus) and its susceptibility to Aeromonas hydrophila infection

Abstract

In the present study, goldfish (Carassius auratus) were fed diets supplemented with different levels of methanolic crude extracts of Andrographis paniculata to assess their efficacy against Aeromonas hydrophila. The A. paniculata extract showed antibacterial activity against A. hydrophila at different concentrations and was characterised by FTIR and GC-MS analysis. The fishes (C. auratus) were divided into three groups, the control fishes were fed with a basel diet, the DI and DII group fishes were fed with a basel diet mixed with 0.1% and 1% of methanolic crude extracts of A. paniculata, respectively for 4 weeks. Then, haematological and immunological parameters were examined in each experimental and control group after the 2nd and 4th week. Finally, all group fish were challenged with A. hydrophila at the end of the 4th week, and their cytokine genes expression were investigated. The results showed that even at low concentrations (50 μg) of A. paniculata leaf extracts showed a potent antibacterial effect against A. hydrophila. GC-MS analysis revealed that the methanol precipitation contains Benzylamine, 2-hydroxy-N,N-DI-[2-aminoethyl]-, 18-Nonadecen-1-OL, and andrographolide. Similarly, FTIR analysis revealed aliphatic primary amine, conjugated ketone and alcohols, which are known antimicrobials. The extracts also changed the growth, haematological and immunological parameters of treated fishes by significantly increased the total RBC counts and haemoglobin level, along with the phagocytic, total immunoglobulin and myeloperoxidase activities when compared to the BD group. Moreover, fish fed with 1% of A. paniculata extract showed a higher survival rate (80%) against A. hydrophila. Furthermore, 1% of A. paniculata extract dietary was significantly up-regulated pro-anti-inflammatory cytokine gene expression, compared with the BD group. In conclusion, dietary A. paniculata extract supplementation beneficial for C. auratus, as it assesses their efficacy against A. hydrophila.