The Importance of Dietary Antioxidants on Oxidative Stress, Meat and Milk Production, and Their Preservative Aspects in Farm Animals: Antioxidant Action, Animal Health, and Product Quality—Invited Review

SIMPLE SUMMARY: Oxidative stress occurs within biological systems when free radicals, classified as reactive oxygen species and reactive nitrogen species, are in excess. The reactions between free radicals and other micro-macro-molecules have some benefit but more generally, have been associated with subclinical disease development and suppressed farm animal performances. Subsequently, this may lead to animal-sourced food products having lower quality and shorter shelf-life (off-farm, e.g., meat and milk products). Free radicals are generated from regulated and unregulated sources (e.g., mitochondrial respiration, enzymatic activities, electron leakage), and their responsiveness to environmental and nutritional stressor events overwhelms the antioxidant defenses in the body maintain redox homeostasis, thus leading to oxidative distress. Research has demonstrated that dietary antioxidants may be used to redress redox imbalance and that, in this function, bioactive compounds will offer different efficacies and effects both on- and off-farm. Important dietary antioxidants include vitamins, trace elements, some fatty acids, and phytonutrients, such as beta-carotene, polyphenols, flavonoids, etc. These may be sourced via the feeds, supplements, and forages provided to farm animals, available from natural or synthetic (additive) sources. Antioxidant accumulation within body tissues of farm animals can support better animal performance and improved meat and milk quality with extended shelf-life. Once consumed, these enriched products may help ameliorate human oxidative stress. These were the topics of this review below. ABSTRACT: The biological effects of oxidative stress and associated free radicals on farm animal performance, productivity, and product quality may be managed via dietary interventions—specifically, the provision of feeds, supplements, and forages rich in antioxidants. To optimize this approach, it is important first to understand the development of free radicals and their contributions to oxidative stress in tissue systems of farm animals or the human body. The interactions between prooxidants and antioxidants will impact redox homeostasis and, therefore, the well-being of farm animals. The impact of free radical formation on the oxidation of lipids, proteins, DNA, and biologically important macromolecules will likewise impact animal performance, meat and milk quality, nutritional value, and longevity. Dietary antioxidants, endogenous antioxidants, and metal-binding proteins contribute to the ‘antioxidant defenses’ that control free radical formation within the biological systems. Different bioactive compounds of varying antioxidant potential and bio-accessibility may be sourced from tailored feeding systems. Informed and successful provision of dietary antioxidants can help alleviate oxidative stress. However, knowledge pertaining to farm animals, their unique biological systems, and the applications of novel feeds, specialized forages, bioactive compounds, etc., must be established. This review summarized current research to direct future studies towards more effective controls for free radical formation/oxidative stress in farm animals so that productivity and quality of meat and milk can be optimized.