Dietary Antioxidants and Nrf2-Related Redox Responses in Sheep: Evidence, Limitations, and Implications for Health and Productivity

Abstract

Simple Summary Sheep encounter oxidative challenges during late gestation, lambing, early life, weaning, rapid growth, lactation, reproduction, disease, and heat exposure. The Nrf2–Keap1–antioxidant response element (ARE) system helps cells adapt by regulating antioxidant, detoxification, and repair processes. Dietary antioxidants may support this system, but the sheep-specific evidence must be interpreted cautiously. Only two dietary studies in sheep have measured Nrf2-related molecular readouts directly, and both show pathway-associated changes rather than causal proof of Nrf2 activation. Most other sheep studies report antioxidant-enzyme activities, oxidative-damage markers, health outcomes, or product quality without measuring the pathway. This review separates those evidence levels, summarizes practical benefits and limitations, and identifies the experiments needed before Nrf2-targeted feeding can be recommended reliably. Current evidence supports context-specific antioxidant nutrition, particularly during documented oxidative challenge, but not the assumption that every antioxidant supplement works through Nrf2 or improves productivity.