Effect of α-tocopherol supplementation on in vitro maturation of sheep oocytes and in vitro development of preimplantation sheep embryos to the blastocyst stage

Purpose To determine the effects of alpha-tocopherol supplementation to oocyte maturation media and embryo culture media on the yield of ovine embryos. Methods alpha-tocopherol, at concentrations of 0, 50, 100, 200, 400 and 500 mu M was supplemented to ovine oocyte or embryo culture media and cultured at 5% or 20% 02 levels. Percentages of cleavage, morula and blastocyst, total cell count and comet assay were taken as indicators of developmental competence of embryos. Results 200 mu M alpha-tocopherol in embryo culture medium at 20% O(2) level significantly increased the rates of cleavage (P < 0.05), morulae (P < 0.05) and blastocyst (P < 0.01) formation and blastocyst total cell number (P < 0.01) when compared with control. The rates of blastocyst formation were also significantly higher in 100 mu M (P < 0.01) and 400 mu M (P < 0.05) supplemented groups than control. Conclusion alpha-tocopherol supplementation may enhance the in vitro developmental competence of ovine embryos by protecting them from oxidative damage.