Dietary coriander (Coriandrum sativum L) oil improves antioxidant and anti-inflammatory activity, innate immune responses and resistance to Aeromonas hydrophila in Nile tilapia (Oreochromis niloticus).

The use of essential oils (EOs) as a natural alternative to antibiotics for disease prevention strategies is gaining much interest in recent decade. Coriander (Coriandrum sativum L.) essential oil is rich in bioactive compounds like linalool and geranyl acetate which have antioxidant, anti-inflammatory and antimicrobial activities. The present work was proposed to evaluate the inclusion levels of coriander oil in tilapia feed to enhance tilapia health and resistance to bacterial infection. Five iso-nitrogenous and iso-lipidic feeds were prepared with graded levels of coriander oil (0, 0.5, 1, 1.5 and 2%). The fish were then fed with the five experimental diet twice daily for a period of 60 days in triplicate. Haemoglobin, mean corpuscular volume, mean cell haemoglobin increased significantly in the coriander oil treated groups. The thrombocyte count was more in 2% inclusion level. The superoxide dismutase activity increased significantly in all the treated groups. The feeds with 1.5 and 2% coriander oil showed increased respiratory burst and myeloperoxidase activities while lysozyme and antiprotease activities were significantly higher in 1, 1.5 and 2% dietary treatments compared to control. The survival increased in dose dependent manner post challenge with an intraperitoneal injection of Aeromonas hydrophila at a LD dose of 5 × 10 cfu mL. The feed containing 1, 1.5 and 2% of coriander oil showed 89, 100 and 100% survival respectively compared to 39% in control diet. The expression level of IgM and IL-8 increased significantly post challenge with A. hydrophila in coriander oil fed groups. The expressions of TNFα, IL-1β, TGFβ and HSP 70 genes, however, decreased significantly in the treated groups compared to control. Histopathological examination of spleen showed large melano-macrophage centers in control and 0.5% coriander fed group with signs of necrosis and vacuolation post A. hydrophila infection, whereas 1, 1.5 and 2% treated groups showed normal architecture of spleen. From the above observations it can be concluded that coriander oil with 1% incorporation in feed improves tilapia health and resistance to bacterial infection.