Onion extract and grape seed powder as antioxidants to improve growth: Evidence from studies with oxidative stressed intestinal and liver cells as well as growing broilers

Background Oxidative stress negatively impacts the growth, health, and overall welfare of animals. Plant extracts have great potential in mitigating oxidative stress. This study aims to evaluate the antioxidant capacities of onion extract and grape seed powder in vitro, and the potential benefits of a polyphenol product (obtained from onion and grape among other plant sources) in vivo. Then it further evaluates the effect of polyphenol product partial replacement of synthetic vitamin E on the growth performance of Ross 308 broilers. Results Results showed that tert‐Butyl hydroperoxide treatment reduced cell viability, adenosine 5'‐triphosphate content, and mitochondrial membrane potential in intestinal epithelial cells, and enhanced intracellular reactive oxygen species production. Onion extract and grape seed powder pretreatment could reverse the oxidative damage. The antioxidant potential assay showed good antioxidant performance of the polyphenol product in Leghorn Male Hepatoma cell line. The results revealed significant differences in body weight, average daily weight gain, and feed conversion ratio between the treatment group, replacing 50% of vitamin E with the polyphenol product and the control; the polyphenol product group performed as well as the standard vitamin E group, indicating potential benefits of polyphenol product supplementation. Conclusion Onion extract, grape seed powder, and polyphenol product have great potential in mitigating oxidative stress and improving growth. The in vivo study suggests that supplementing broiler diets with polyphenol product can partially replace synthetic vitamin E in broiler chicken diets.