The effect of dietary eugenol nano-emulsion supplementation on growth performance, serum metabolites, redox homeostasis, immunity, and pro-inflammatory responses of growing rabbits under heat stress

Background: Heat stress (HS) is a main abiotic stress factor for the health and welfare of animals. Recently, the use of nano -emulsion essential oils exhibited a promising approach to mitigate the detrimental impacts of abiotic and biotic stresses, ultimately contributing to the global aim of sustainable livestock production. Aim: The current study was piloted to assess the impact of eugenol nano -emulsion (EUGN) supplementation on growth performance, serum metabolites, redox homeostasis, immune response, and pro -inflammatory reactions in growing rabbits exposed to HS. Methods: A total of 100 male weaning rabbits aged 35 days were divided into 4 treatments. Rabbits were fed the diet with EUGN at different concentrations: 0 (control group; EUGN0), 50 (EUGN50), 100 (EUGN100), and 150 (EUGN150) mg/kg diet for 8 weeks under summer conditions. Results: Dietary EUGN levels significantly improved ( p < 0.05) the body weight, body weight gain, carcass weights, and improved feed conversion ratio of rabbits. EUGN supplementation significantly increased Hb, platelets, and red blood cells , while the mean corpuscular hemoglobin and eosinophils were significantly decreased compared to the control one. Compared with EUGN0 stressed rabbits, all EUGN-experimental groups had a reduction in levels of total glycerides ( p < 0.01), uric acid, total bilirubin, direct bilirubin, and gamma-glutamyl transpeptidase ( p < 0.01). Total antioxidant capacity and glutathione peroxidase were significantly improved by EUGN treatment when compared to the control one ( p < 0.01), while the EUGN100 exhibited the greatest levels of catalase. Lipid peroxidation (malondialdehyde) was significantly decreased in EUGN-treated groups. All pro -inflammatory cytokines serum interleukin 4, Interleukin 1 beta, and tumor necrosis factor alpha were considerably decreased after dietary EUGN supplementation ( p < 0.05). The serum concentrations of immunoglobulins (IgG and IgM) were significantly improved in rabbits of the EUGN150 group. Conclusion: This study shows that EUGN can be used as a novel feed additive to enhance the growth performance, immune variables, and antioxidants, and reduce the inflammatory response of growing rabbits exposed to thermal stress.