Polyunsaturatd fatty acids, lipid peroxidation and antioxidant protection in avian semen.

Avian spermatozoa are characterised by high concentrations of polyunsaturated fatty acids (PUFAs), in particular docosatetraenoic (DTA, 22:4n-6) and arachidonic (AA, 20:4n-6) acids. As a result they are vulnerable to lipid peroxidation, which is considered to be an important factor of male infertility. Antioxidant systems are expressed in spermatozoa and seminal plasma and build three major levels of antioxidant defense. The first level is based on the activity of superoxide dismutase (SOD) which is, in conjunction with glutathione peroxidase (GSH-Px), catalase and metal-binding proteins, responsible for prevention of free radical formation. The second level of defence is responsible for prevention and restriction of chain reaction propagation and includes chain-breaking antioxidants such as vitamin E, ascorbic acid, glutathione and some others. The third level of antioxidant defence deals with damaged molecules, repairing or removing them from the cell and includes specific enzymes such as lipases, proteases, DNA repair enzymes etc. In the review, profiles of PUFAs and the two first lines of antioxidant defence in avian spermatozoa are characterised. Dietary manipulation of the breeder''''s diet (PUFA, vitamin E and selenium) as an effective means of modulating fatty acid composition and antioxidant system is also considered. Antioxidant properties of seminal plasma and efficiencies of inclusion of antioxidants into semen diluents are also characterised.