Effect of α-Tocopherol on Bovine In Vitro Fertilization

The objectives of this work are to determine if exogenous supplementation with alpha-tocopherol increases the in vitro fertilization (IVF) rate of bovine oocytes and improves viability of selected spermatozoa after 'swim-up'. The percentage of fertilized oocytes was significantly but negatively correlated (r = -0.941, p < 0.01) with the concentration of alpha-tocopherol. The control resulted in 95% of fertilized oocytes, which decreased as follows: 25 mu M alpha-tocopherol (alpha 25) 86%, 50 mu M alpha-tocopherol (alpha 50) 74%, 100 mu M alpha-tocopherol (alpha 100) 66% and 200 mu M alpha-tocopherol (alpha 200) 56%. Relatively to sperm viability after 'swim-up' with alpha-tocopherol supplementation, this antioxidant proved to have a beneficial effect as its concentration increased up to alpha 50, decreasing for the concentrations of alpha 100 and alpha 200. Control resulted in 83% of live cells and 16% of dead cells; alpha 25 resulted in 88% of live cells and 12% of dead cells; alpha 50 resulted in 91% of live cells and 9% of dead cells; alpha 100 resulted in 67% of live cells and 33% of dead cells; and finally alpha 200 resulted in 57% of live cells and 42% of dead cells. In summary, the present study allows to conclude that, in our conditions, supplementation with the antioxidant alpha-tocopherol in IVF of bovine oocytes has a detrimental effect on fertilization rates. Nevertheless, exogenous supplementation with alpha-tocopherol at a concentration of 50 mM in the sperm-TALP media during the 'swim-up' technique has a significant beneficial effect on the selected spermatozoa viability.