Effects of Grape By-Products on Oxidative Stress and Inflammation in Farm Animals: An Overview of Studies Performed in Pigs, Chickens, and Cattle.

High-yielding farm animals often face severe metabolic stress, compounded by environmental stressors such as psychosocial stress, heat stress, intensive housing systems, and poor hygiene management. These factors result in oxidative stress and inflammatory processes, which adversely affect both animal health and performance. Polyphenols are known to alleviate both oxidative stress and inflammatory responses. Since grapes are rich in polyphenols, by-products of winemaking could have beneficial effects on these processes. This review aims to provide an overview of the potential antioxidative and anti-inflammatory effects of grape by-products in farm animals. The first section of the review examines the causes and consequences of oxidative stress and inflammation. The second section highlights the general effects of polyphenols in addressing these issues. The third and central part of the review presents an overview of findings from studies investigating the impact of various grape-derived polyphenols on the antioxidant system and inflammation in pigs, chicken, and cattle. Overall, these studies demonstrate that grape by-products can effectively reduce oxidative stress and inflammation in pigs and chickens, often leading to improved performance. In cattle, however, fewer studies have been conducted, and the results regarding oxidative stress and inflammation are less consistent. In conclusion, grape by-products represent valuable feed options for preventing oxidative stress and inflammation in monogastric farm animals (pigs, chickens).