Gamma-oryzanol dose optimization in maturation or culture media for in vitro ovine oocyte and embryo development.

Abstract.

Background: The efficiency of ovine in vitro embryo production remains low yet.

Aims: The present study evaluated the effect of different concentrations of gamma (γ)-oryzanol in maturation or culture media on in vitro ovine oocytes and embryo developments.

Methods: Morphologically normal COCs were aspirated from ovine ovaries, subjected to maturation media supplemented with 0, 2.5, 5, 10, 20, 50, and 100 μM γ-oryzanol, then processed for conventional in vitro fertilization and culture to assess their potential to cleave and develop to blastocyst. Another group of COCs was matured and fertilized. Presumptive zygotes were subjected to culture in drops of media supplemented with 0, 2.5, 10, 20, and 50 μM γ-oryzanol, and the developments of embryos were assessed under 7% and 20% O₂ levels. A control group of no supplementation was included in each experiment.

Results: The expansion of cumulus cover and survival rate tended to decrease with concentrations of 20, 50, and 100 μM in maturation media, suggesting an overdose effect. The cleavage and total blastocyst rates were significantly higher for oocytes matured at 5 μM γ-oryzanol. The presumptive zygotes cultured in supplemented media showed significantly higher cleavage and total blastocyst rates with concentrations of 5 and 10 μM γ-oryzanol (P<0.04) in both 7% and 20% O₂ levels.

Conclusion: These results represent the first study showing a significant positive effect of the γ-oryzanol supplement on in vitro ovine oocyte and embryo development, at optimal concentrations of 5 μM in maturation, and 5 and 10 μM in embryo culture media.