Potential of plant polyphenols to combat oxidative stress and inflammatory processes in farm animals
Since the ban of feed antibiotics by the EU in the year of 2006, there is intensive search for feed additives in farm animals which are able to maintain or even improve animal health and animal performance. Natural compounds produced by plants might be relevant candidates in this respect. Plants are producing a great variety of secondary metabolites. Many of these secondary plant metabolites have been shown to exert a broad range of beneficial effects on health in humans and rodent models (e.g. Cornwell et al., 2004; Hooper et al., 2008; Lavecchia et al., 2013; Martin and Bolling, 2015). Among the great number of secondary plant metabolites, the group of polyphenols might be most promising due to its well‐established antioxidative and gene regulatory properties (Baur et al., 2006; Chuang and McIntosh, 2011; Aguirre et al., 2014). It has been well established that polyphenols are able to act antiinflammatory both in vitro and in vivo by inhibiting the activation of nuclear factor kappa B (NF‐κB) and to induce antioxidative and cytoprotective effects by inducing nuclear factor erythroid 2‐related factor‐2 (Nrf2) (Rahman et al., 2006; Scapagnini et al., 2011; Tangney and Rasmussen, 2013). In humans and experimental animal models, these effects of plant polyphenols are well established. In contrast, in farm animals, the effects of plant polyphenols with respect to their antiinflammatory, antioxidative and cytoprotective effects have been less investigated so far. This study aims to give a comprehensive overview about effects of polyphenols in farm animals with major emphasis on the effect of polyphenols on inflammation and oxidative stress, both of which are linked with each other. In the first chapters, however, the role of oxidative stress and inflammation in farm animals is highlighted.