Holding temperature to transport immature bovine oocytes in collection media critically affects their developmental...

We investigated the holding condition in collection media to establish transportation system of immature bovine cumulus-oocyte complexes (COCs). We examined holding temperature (38°C or 20°C), basal media (Lactated Ringer's solution and TCM199) and supplementation of hypoxanthine, an inhibitor of meiotic resumption. As a result, no blastocyst was obtained from COCs held at 38°C for 6 h or longer, whereas blastocysts were obtained even after 24 h holding in all experimental groups held at 20°C. The blastulation rate was maintained (42%) in TCM199 with hypoxanthine group even after 12 h holding, while reduction of the blastulation rates were observed in all other groups (P < 0.05). After 24 h of storage, Lactated Ringer's solution without hypoxanthine showed the highest blastulation rate (40%). In conclusion, holding temperature of oocytes critically affects the developmental competence of oocytes, and oocytes held at 20°C maintain their developmental competence for at least 12 h.