Selenium in poultry nutrition 2. Reproduction, egg and meat quality and practical applications

In the first part of this review (Surai, 2002), the antioxidant properties and pro-oxidant activity of Se have been described. In spite of a long history, our knowledge of the molecular mechanisms of Se action in human and animals are still in their initial stages. Indeed Se is an integral part of various selenoproteins with glutathione peroxidase (GSH-Px) being the first selenoprotein identified in 1973. Se's participation in antioxidant defence and in the regulation of redox status of the cell could explain its importance to various physiological functions, especially to reproduction. Chicken embryo tissues and spermatozoa are rich in long chain polyunsaturated fatty acids (PUFA) and as a result are very vulnerable to lipid peroxidation. Therefore Se is a crucial factor in maintaining appropriate antioxidant defence during embryonic development and spermatogenesis. In conditions of stress in commercial poultry production the beneficial effects of Se are difficult to overestimate. From egg storage before incubation, when lipid peroxidation can occur, to the final day of egg production, Se participates in preventing the damaging effects of free radicals and toxic products of their metabolism. Dietary antioxidant supplementation in general and organic Se supplementation in particular are considered to be major protective measures for maintaining high productive and reproductive characteristics in poultry.