Combined effect of DHA and alpha-tocopherol enrichment on quality and susceptibility to oxidation in chicken spermatozoa

The aim of this study was to investigate the effect of n-3 PUFA (n-3) and vitamin E rich diets on quality and phospholipid fatty acid composition of chicken spermatozoa. Chicken broiler breeders received a control diet supplemented with soybean oil (CO), rich in C18:2n-6, or a diet supplemented with fish oil (FO), rich in C22:6n-3 (DHA). Both oil inclusions (1% wt/wt) were carried out in combination with two levels of dl-alpha-tocopheryl-acetate (vitamin E), 100 (standard requirement) and 300mg/Kg of feed, therefore 4 experimental groups were considered: CO100, CO300, FO100 and FO300. Semen samples were routinely collected, pooled per treatment and diluted 1+1 in Lake diluent. The following semen parameters were measured: concentration (106/ml), motility (%), forward progressive motility (FPM), damaged cells (%), sperm alha-tocopherol (ng/109cells), sperm susceptibility to induced oxidation (microgrammi MDA/109cells) and sperm phospholipid bound fatty acid composition (%). Quality of cell movement (i.e. FPM) was significantly increased in the FO group and the combination of FO with 300mg/Kg vitamin E caused also an increase of the proportion of motile cells. The proportion of damaged cells was increased in the FO group. Interestingly, the proportion of live cells was significantly higher in the FO300 vs the FO group. The sperm content of alpha-tocopherol was significantly increased as a consequence of dietary vitamin E supplementation. Spermatozoa from FO group were significantly less resistant to induced oxidation in comparison to the other groups. The supplementation with only 1% FO had a high effect on the proportion of C22:6n-3 (6.29 vs 3.43%) in sperm phospholipid followed by a decrease in the ratio n-6/n-3 (4.45 vs 11.90). The higher supplementation with vitamin E significantly increased the proportion of C22:4n-6, whatever the dietary fatty acid composition. These results suggest that the ratio n6/n3 in commercial diets should be manipulated in favour of the n-3 PUFA family and, as a consequence, the antioxidant supplementation should be increased according to the new sperm lipid composition.