Dose-response curves for the effects of eucalyptus essential oil nanoemulsion on growth performance and health status of heat-stressed growing rabbits

Objective: Dose-response curves were performed to explore the effect of eucalyptus essential oil nanoemulsion (EEONE) on the growth rate, feed efficiency, and health status of growing rabbits facing heat stress. Methods: Sixty growing rabbits (6 weeks old), were randomly divided into four homogeneous groups, receiving diets supplements with 0, 100, 200, and 400 mg EEONE/kg diet (EEONE0, EEONE100, EEONE200, and EEONE400, respectively). Results: Significant improvements were observed in growth performance, feed utilization, and physiological responses in the EEONE-treated groups compared to the control (p<0.05). Regression analysis revealed quadratic increases in red blood corpuscles and quadratic decreases in white blood cell counts in response to EEONE treatment, with optimal concentrations showed at 325 and 300 mg EEONE, respectively. Hemoglobin concentration, platelet count, blood protein and glucose levels linearly increased, while liver enzymes decreased significantly due to the EEONE treatment. The aberrant changes observed in liver tissues due to heat stress were effectively reversed, leading to a restoration of hepatic morphology closely resembling normal conditions, by co-administration of EEONE. Serum urea and creatinine concentrations decreased quadratically in the EEONE-treated groups, minimizing at 300 mg EEONE. Quadratic regression analysis indicated that the optimal doses were 300 mg EEONE for glutathione peroxidase and protein carbonyl, and 350 mg EEONE for total antioxidant capacity and malondialdehyde. Cellular and humoral immunity as well as pro inflammatory cytokinase significantly improved by the dietary treatment. Conclusion: Supplementing the diet with EEONE at levels of 300-400 mg can effectively improve growth metrics and health status of fattened rabbits.