In this study, we evaluated the effects of holding in vitro- produced bovine blastocysts under mild hypothermia (33°C or 35°C), by examining viability and hatching rates of day 7 blastocysts (day 0: in vitro fertilization) cultured for 6 days and transcriptional expression of cold-inducible transcription factors Cirp and Rbm3 , implicated in mild hypothermia-induced cellular protection against various types of stress. In the normothermic control (38.5°C), viability of the embryos decreased rapidly after day 10, and most samples were degenerated on day 13. However, mild hypothermia, particularly at 33°C, resulted in maintenance of high embryonic survival rates until day 13 (77.1% on day 13) and significant increases in transcriptional expression of Rbm3 in day 11 embryos compared with those at 38.5°C. Thus, our results suggested that upregulation of Rbm3 may occur in response to mild hypothermia in many bovine embryos, providing insights into the effects of mild hypothermia on embryo quality.

Purpose Dimethyl α‐ketoglutarate (dm‐α‐KG) promotes in vitro development to blastocysts of C57BL/6J X C3He F1 mouse zygotes cultured in medium lacking pyruvate. Here, we examined the effects of pyruvate and dm‐α‐KG on in vitro development to blastocysts of ICR mouse zygotes and their post‐implantation developmental ability. Methods Zygotes were cultured in medium with pyruvate at 0‐0.2 mmol/L in the presence or absence of 1 mmol/L dm‐α‐KG for 96 hours and evaluated for blastocyst formation rates. The resultant blastocysts were non‐surgically transferred to surrogates and evaluated for birth rates. Results In medium lacking pyruvate, zygotes could not develop beyond the two‐cell stage, in the presence or absence of dm‐α‐KG. However, the blastocyst formation rate in medium with 0.01 mmol/L pyruvate (12%) was markedly increased with addition of dm‐α‐KG (49%). Around 80% of embryos developed to blastocysts in medium with 0.2 mmol/L pyruvate, in the presence or absence of dm‐α‐KG. Importantly, birth rate was markedly improved by treatment with 0.2 mmol/L pyruvate and dm‐αKG (31.0%), compared with those with pyruvate treatment alone (16.3%). Conclusions Pyruvate and dm‐α‐KG synergistically work during in vitro culture to markedly improve the blastocyst formation rate and post‐implantation developmental ability of the resultant blastocysts in ICR mice.