The Role of Methionine Supplementation on Oxidative Stress and Antioxidant Status of Poultry-A Review

The physiological status of poultry can be disturbed by different stressors that may lead to oxidative stress conditions. Oxidative stress activates defense systems, which mitigates the adverse effects. Several lines of the poultry defense system exist, including enzyme systems such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and non-enzymatic antioxidants such as Glutathione (GSH). Methionine—a vital amino acid in poultry nutrition—plays a significant role in protein synthesis, transsulfuration, and transmethylation and is also involved in several biochemical pathway activations that can affect the antioxidant system. Therefore, this review aims to summarize the current knowledge on the role of methionine in poultry under heat stress or managing stress, on the antioxidants responsible for scavenging free radicals (GSH) and those responsible for detoxification (SOD, CAT, and GPx). Different levels of methionine supplementation above the requirement (up to 1% Met added on the basal diet) have been tested on the antioxidant status of poultry. It has been shown to improve the antioxidant status and reduce oxidative stress. The results of many experiments on poultry supplemented with diets of different methionine sources indicate that L-Met has good potential to stimulate the antioxidant status of poultry.