Effects of Laurus nobilis essential oil nano-particles on growth performance, antioxidant and immune responses to bacterial infection in Nile tilapia, Oreochromis niloticus

Abstract

This study was designed to assess the effects of four feeds containing 0 (CTL), 25 mg/kg (LN25), 50 mg/kg (LN50) and 100 mg/kg (LN100) Laurus nobilis (LN) essential oil nano-liposomes (LN-NP) on Nile tilapia, Oreochromis niloticus. After 56 days of feeding with the above diets, growth performance and digestive enzyme activities determined in all treatments. Then, the fish were experimentally infected by Aeromonas hydrophila and their survival, antioxidant capacity, biochemical parameters and immune-related transcripts were measured, before and after the infection. The results showed that the growth rate and intestinal activities of amylase, lipase and protease were significantly higher in the LN50 and LN100 treatments than CTL. Post-infection survivals in the LN50 and LN100 treatments were similar and significantly higher than the CTL and LN25 treatments. Compared to the CTL treatment, the LN50 and LN100 treatments showed improved hepatic antioxidant parameters and lower malondialdehyde levels before and/or after infection. Infection significantly decreased plasma lysozyme and complement activities, but the LN50 and LN100 treatments had significantly higher activities before and after infection. These treatments had lower alanine aminotransferase and aspartate aminotransferase activities in plasma before and after infection, compared to the CTL treatment. The expression of tumor necrosis factor-alpha, interleukin-8 and interleukin-1 beta increased significantly in the LN50 and LN100 treatments, before and after infection, when compared to the CTL treatment. Based on the results, LN-NP at a dosage of 50 mg/kg is suitable for feeding Nile tilapia as it is a growth promoter and immunostimulator and increases the resistance of fish to A. hydrophila.