Development of bovine embryos in KSOM with added superoxide dismutase and taurine and with five and twenty percent O2

Abstract

To further define requirements for embryo development without the assistance of complex media, serum, or coculture, the effects of 5% and 20% O2 concentrations, superoxide dismutase (SOD) (experiment 1), and taurine (experiment 2) were tested in a simple culture medium (KSOM modified with 2.5 mM HEPES). Bovine embryos were produced by in vitro maturation (IVM) and in vitro fertilization (IVF) of oocytes. After fertilization, embryos were cultured in 5% O2:5% CO2:90% N2 at 39°C for the first 40-44 h; then embryos with 4 to 8 cells were cultured in different treatments for another 6 days. Percentage development subsequently was based on this number. In experiment 1, more blastocysts were produced in 5% O2:5% CO2:90% N2 (37%) than in 20% O2:5% CO2:75% N2 (18%; p < 0.01). Blastocyst development with 0, 300, and 600 U/ml of SOD, respectively, was 26%, 26%, and 30% (p > 0.05). In experiment 2, more blastocysts were formed in 5% O2 (39%) than in 95% air (30%; p < 0.05). Also, with 20% O2 and 0, 7, and 14 mM taurine in the medium, blastocyst formation was 18%, 35%, and 36% (p < 0.05). However, in 5% O2, 7 and 14 mM taurine was not beneficial (p = 0.99), as 39% blastocysts were formed with no taurine. In conclusion, results from both experiments demonstrated that 5% O2 was superior to 20% O2 for development of IVM/IVF bovine embryos. SOD had no effect in either 5% or 20% O2. However, 7 mM and 14 mM taurine counteracted the negative effect of 20% O2. The best culture system tested here was simple; it resulted in sufficient blastocyst formation that it can serve as an excellent base for further studies of the requirements of embryos.