Protein oxidation in feed: Occurrence, monitoring, and mitigation strategies

Protein oxidation is defined as a covalent modification caused by reactive oxygen species (ROS) or secondary oxidized by-products. The mechanisms and influences of protein oxidation on animal-derived food quality have been studied for many years, but its effects on feedstuff and animal health are largely unknown. Protein oxidation causes oxidation in both amino acid side chains and protein backbones, resulting in the formation of harmful substances and a decrease in nutritional value. Excessive levels of protein oxidation in animal diets have been associated with various biological consequences in animals, including reduced growth performance, compromised antioxidant capacity, immune disorders, and intestinal digestion and absorption, and antioxidant capacity. Protein oxidation in feeds can be detected by various methods such as spectrophotometric assay and fluorescence spectroscopy and controlled by several approaches such as supplementation of antioxidants and nutrition regulation. In this review, the basic principles of protein oxidation and its detection methods, effects on animals, and preventive strategies are discussed.