Tiny but Mighty: A Low Dose of Standardized Dry Grape Extract Potentiates Antioxidant Defenses in Broiler Chickens

Oxidative stress can impair poultry health and performance, underscoring the importance of enhancing endogenous antioxidant defenses as a nutritional strategy. Although plant-derived polyphenols have shown antioxidant potential, their efficacy remains inconsistent owing to variability in extract composition and the frequent evaluation of doses exceeding those authorized for commercial use. This study investigated the effects of dietary supplementation with a standardized dry grape extract (SDGE, Nor-Grape^®, Nor-Feed, France) at an authorized inclusion level (30 mg/kg feed) on growth performance and antioxidant status in broiler chickens under commercial production conditions. A total of 756 one-day-old male Ross 308 broilers were randomly allocated to a control diet (CTL, n = 392) or the same diet supplemented with grape extract (NG, n = 364) for 35 days. Growth performance was recorded throughout this study, and blood samples collected on days 11 and 35 were analyzed for total antioxidant capacity (TEAC), lipid peroxidation (TBARS), and the activities of the endogenous antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). Compared with controls, NG birds exhibited greater final body weight (+71.9 g; p < 0.001) and improved FCR during the finisher phase (p < 0.05). Supplementation significantly enhanced systemic antioxidant capacity and endogenous antioxidant enzyme activities while reducing lipid peroxidation, indicating improved oxidative status. These findings demonstrate that SDGE supplementation at commercially authorized inclusion levels effectively enhances antioxidant defenses and improves production performance in broiler chickens.