The aim of the present study was to optimize the temperature for the temporal storage of
matured bovine oocytes. In vitro–matured bovine oocytes were preserved in HEPESbuffered
TCM199 medium supplemented with 10% newborn calf serum at different temperatures
(4 C, 15 C, 25 C, and 38.5 C) for 20 hours. Embryo development and blastocyst
quality after in vitro fertilization, cytoplasmic ATP and glutathione levels in oocytes, and
the frequency of apoptotic oocytes were compared among storage groups and a control
group without storage. Among the storage groups, those at 25 C and 38.5 C showed the
highest rates of blastocyst development (19.3% and 24.5%, respectively) compared with
those stored at 4 C and 15 C (8.5% and 14.9%, respectively); however, blastocyst formation
rates in all storage groups were lower than that in the control group (39.8%; P < 0.05).
Storage at 38.5 C and 15 C was associated with reduced cell numbers in resultant blastocysts
compared with the control and the 25 C storage groups. Storage at 4 C reduced
metabolic activity of oocytes characterized by their lower ATP levels compared with the
other groups. Storage for 20 hours significantly reduced the glutathione content in oocytes
in all groups in a similar manner, irrespective of the temperature. Storage at 4 C or 15 C
but not at 25 C and 38.5 C significantly increased the percentage of apoptotic oocytes
compared with the control group. In conclusion, 25 C was found to be the most suitable
temperature for the temporal storage of matured bovine oocytes regarding both the
developmental competence of oocytes and the quality of resultant blastocysts.