Use of antioxidants as adaptogens fed to pigs (Sus scrofa domesticus Erxleben, 1777) (meta-analysis)

The meat flash quality is basically dependent on muscle tissue characteristics. Feeding disorders and stresses can cause myopathy, a destabilizing factor of farm animal meat quality. The muscle tissue injury preventing is of particular interest as it can improve lifetime meat quality formation. Dietary enrichment of farm animal nutrition with natural adaptogens and antioxidants offers potential to reduce myopathies of various etiologies. This paper is an overview of nutrition factors as protective agents under stress loads and myopathies in intensively growing pigs. Dietary adaptogens, e.g. selenium, tocopherol, quercetins, etc., inhibit peroxidation of lipids, generation of reactive oxygen species and are important for the control of glycolysis and oxidative stress. Most adaptogens are antioxidants, they have a beneficial effect on the cardiovascular system, including blood capillaries, prevent damage to cell membranes caused by free radicals and apoptosis. The beneficial effects of vitamin E-enriched diets (from 10 to 1000 mg/kg feed, approximately 200 mg/kg mainly) on porcine meat quality characteristics have been well studied in pig breeds and breed combinations during various periods of growing. However, no effect of dietary vitamin E on the growth rate of animals has also been reported. Feed enrichment with dietary tocopherol leads to its deposition in all tissues and organs, primarily in the blood, liver, heart, and in muscle and fat tissues. Vitamin E has a membrane-stabilizing effect, reduces oxidation of membrane lipids, increases the total amount of fatty acids in mitochondria, antioxidant capacity and muscle glycogen content. It has been shown that in pigs fed diets supplemented with vitamin E during fattening phase the vitamin E deposition level in meat is higher. This, in turn, improves meat taste and flavor, reduces the smell characteristic of reheated dishes, does not change the aldehyde profile of meat volatiles and reduces the accumulation of nitrogenous volatiles resulted from the breakdown of meat proteins during storage, including in a vacuum. Less attention is paid to administration of selenium as an adaptogen. It was shown that selenium combined with higher vitamin E level can neutralize the adverse consequences of hyperthermia in growing pigs and increase free fatty acid content in fat. The organic form of dietary selenium improves the antioxidant status of muscles in pigs. However, selenium has different effects on the oxidation of proteins and lipids during meat storage. In some studies, selenium reduced oxidation; in others, on the contrary, it was proved to be unable to inhibit the accumulation of products of oxidative damage. Two flavonoids quercetin and dihydroquercetin (Taxifolin) are well known for their antioxidant properties. The research articles are mainly deal with quercetin and dihydroquercetin bioavailability and deposition, the impact on antioxidant status and reproductive functions of sows, leveling transportation stress, and pork quality. Quercetin supplements have a pronounced effect at 25-50 mg/kg live weight, dihydroquercetin supplements at 1-3.5 mg/kg live weight. The flavonoids are effective when administered both during the fattening period and before slaughter or transportation. Despite the encouraging reports, little research has focused on the role of these flavonoids in the pork meat quality formation, so further study requires. Quercetin when fed up to 6 months at 2 % of the diet reduced damage to dystrophic skeletal muscle fibers in laboratory animals due to a decrease in reduced production of hydrogen peroxide in mitochondria. Adaptogens and directed muscle tissue development regulators are proposed as potentially key supplements ensuring meat quality under intensive animal husbandry, therefore, further search for and study of bioactive substances which can protect muscle tissues from damaging factors are required.