Modern intensive technologies for handling and growing highly productive animals are accompanied by significant changes in their homeostasis causing stress and adversely affecting their health and the quality of the products obtained from them. Depending on the cause, stress is classified as social (technological), environmental, dietary, and immunological. Various types of stress adversely affect the body and contribute to endocrine, energy balance, and carbohydrate-lipid metabolism disturbances, which adversely affects the animal resistance to diseases, productivity and reproductive characteristics. Stress leads to metabolic disorders and changes in the ratio of muscle and fatty tissues. Every year, the manifestations of antemortem and postmortem pathological changes in the microstructure of animal muscle tissue are increasingly noted. Moreover, the affected structures of muscle fibers are characterized by hyper contraction, disruption of cell membranes, and formation of extracellular protein substance represented by denatured forms of proteins reducing the nutritional value and consumer characteristics of the final product. The use of antioxidants in pig diets, including natural ones, helps to reduce the impact of environmental stress factors on animals and increase their adaptive capacity. This review focuses on the ways to reduce stress and the effect of flavonoids, including quercetin, whose properties have been extensively studied in recent years, in order to increase the resistance of highly productive animals to various stress factors.