Evaluation of the simulated physiological oocyte maturation system for improving bovine in vitro embryo production

The aim of this study was to test the simulated physiological oocyte maturation (SPOM)- adapted system during bovine oocyte maturation to improve embryo development. Oocytes were obtained from follicles of 3 to 8 mm in diameter that were aspirated from ovaries obtained from a slaughterhouse. To verify the effect of the maturation system on in vitro embryo production, the cleavage, blastocyst rates on Days 7 and 8, embryo size, and total cell number were evaluated. The resulting data on embryo development were analyzed by the chi-square test, whereas data on embryo size and total cell number were analyzed by the Kruskal-Wallis test. First, the SPOM system principle was tested in our IVM system, in which 0.01 IU/mL of purified FSH and 10% of fetal calf serum were used during maturation. However, the cleavage and blastocyst rates on Days 7 and 8 were drastically reduced compared with those of the control group (P < 0.05). Increasing the dose of purified FSH to 0.1 IU/mL in the SPOM-adapted system did not affect (P > 0.05) embryo production, which remained lower than that of the control group. When less competent oocytes obtained from 1 to 3 mm follicles were used, the SPOM-adapted system was also unable to improve embryo production. To make the adapted system as similar as possible to the reported system, recombinant FSH was associated with BSA during maturation and embryo culture was performed under low oxygen tension conditions. Nevertheless, a reduction (P < 0.05) in the blastocyst rates was also observed, whereas the size and total cell number were similar to those of the control group (P > 0.05). It can be concluded that an SPOM-adapted system used under different culture conditions does not improve in vitro embryo development.