Effect of leucas aspera against aeromonas hydrophila in nile tilapia (Oreochromis niloticus): Immunity and gene expression evaluation

The present study addressed the effects of Leucas aspera enriched diet in Nile tilapia. Three hundred Nile tilapia were fed Leucas aspera as follows: 0 g kg-1 L. aspera (C-control), 5 g kg-1 L. aspera (T1), 10 g kg-1 L. aspera (T2) and 15 g kg-1 L. aspera (T3). After 30 days of feeding, significant (P<0.05) increase in growth performance was noticed by feeding the fish the T2 diet. Thereafter fish were intraperitoneal injected with Aeromonas hydrophila in challenge test. After 21 days of challenge, highest survival rate (70%) was observed in fish fed the T3 diet followed by fish fed T2 diet (65%). Serum immunological parameters such as phagocytosis, alternative complement activity, respiratory burst activity and lysozyme activity were significantly (P<0.05) enhanced in fish fed all inclusion levels of L. aspera with the maximum activity in fish fed the T2 diet. Hematological parameters were significantly (P<0.05) higher in all groups fed L. aspera diets vs. control fed fish. No histopathological changes in liver were observed in fish fed the T2 diet in the histology study. Gene expression study revealed the upregulation in the expression of COX-2 and GR genes. In conclusion, the current results suggest that dietary administration of L. aspera especially the T2 diet, has beneficial effects in improving immunity and can mitigate the adverse effects of A. hydrophila infection in Nile tilapia.