Effects of Panax ginseng Essential Oil on Immunological and Antioxidant Parameters and Disease Resistance in Rainbow Trout

Background: Disease outbreaks pose a significant threat to the aquaculture industry. The use of supplementary feeds is particularly popular among fish farmers to enhance the fish overall health and combat disease. Objectives: This study aimed to evaluate the effects of dietary ginseng, Panax ginseng, essential oil (GEO), on immunological and antioxidant parameters, as well as disease resistance, in rainbow trout, Oncorhynchus mykiss. Methods: Fish were fed diets containing 0 mL/kg (control; CTL), 0.5 mL/kg (GEO0.5), 1.0 mL/kg (GEO1), 1.5 mL/kg (GEO1.5), 2 mL/kg (GEO2), 2.5 mL/kg (GEO2.5), 3. mL/kg (GEO3), and 3.5 mL/kg (GEO3.5) GEO for 8 weeks, in triplicate. Then, they were experimentally infected with Aeromonas hydrophila. Results: Results indicated that the GEO3 treatment demonstrated the highest levels of serum superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), while the lowest serum malondialdehyde (MDA) levels were recorded in the GEO2 and GEO2.5 groups. Furthermore, the GEO3 treatment resulted in the lowest serum levels of alanine aminotransferase (ALT) and lactate dehydrogenase (LDH), whereas the GEO2 treatment showed reduced serum levels of alkaline phosphatase (ALP) and aspartate aminotransferase (AST). Immunological assessments revealed that the GEO3 treatment had the highest serum and mucus lysozyme and immunoglobulin (Ig) levels, along with elevated serum alternative complement, myeloperoxidase (MPO), and mucus protease activity. Blood respiratory burst activity and mucus ALP were also highest in the GEO2.5 and GEO3 treatments. Notably, the lowest post-infection mortality rate was observed in the GEO3 group. Conclusion: Based on these findings, it is recommended to include 2-3 mL/kg of GEO in trout feed to enhance fish health and disease resistance.