The protective influence of orange essential oil nano-emulsion on growth performance, antioxidant activity, immune status, inflammatory response, and hepato-renal function in heat-stressed growing rabbits

Heat stress (HS) adversely affects rabbit production, reducing growth performance, physiological responses, and farm profitability. Nanoemulsified orange essential oil (NOEO) is a natural antioxidant with anti-inflammatory properties that may mitigate oxidative stress and enhance cellular defense mechanisms. This study evaluated the effects of dietary NOEO on growth performance, blood biochemistry, antioxidant status, immune and inflammatory responses, and liver and kidney histomorphology in heat-stressed rabbits. Forty-eight six-week-old male New Zealand White rabbits (752.91 ± 17.40 g) were randomly assigned to four groups: a control group fed a basal diet and three treatment groups receiving the same diet supplemented with 100, 200, or 400 mg NOEO/kg feed. Heat-stressed rabbits supplemented with NOEO showed significant (p < 0.05) improvements in body weight, feed conversion ratio, and performance index. Blood hematology and serum levels of total protein, albumin, total cholesterol, triglycerides, low-density lipoprotein, and very low-density lipoprotein were also enhanced in all treated groups compared with the control. NOEO supplementation improved antioxidant defenses, as indicated by increased total antioxidant capacity and elevated activities of key antioxidant enzymes (glutathione peroxidase, catalase, and superoxide dismutase), particularly in the NOEO400 treated group (p < 0.05). Nitric oxide levels were significantly higher, while malondialdehyde concentrations were significantly lower in NOEO200 and NOEO400 groups, reflecting reduced oxidative stress (p < 0.05). Immune responses were strengthened, with higher serum IgM and IgA levels, accompanied by downregulation of pro-inflammatory cytokines IL-6 and IFN-γ (p < 0.05). Furthermore, liver and kidney function and tissue structure were improved in NOEO-supplemented rabbits. In conclusion, dietary NOEO, particularly at 400 mg/kg, enhanced growth performance, antioxidant status, immune competence, and hepato-renal health in heat-stressed rabbits, likely through improved cellular defense mechanisms that protect against oxidative and inflammatory damage.