Abstract
The aim of this study was to investigate the effects of pyruvate and serum during the storage of in vitro matured (IVM) bovine oocytes in a medium, on their developmental competence. After IVM for 20 h, bovine oocytes were placed in a 1 ml of a HEPES buffered TCM 199 medium (base medium) in a sealed Eppendorf tube and stored for 20 h at 25°C prior to in vitro fertilization (IVF= Day 0). When the base medium was supplemented with either 10.27 mM pyruvate or 10% (v/v) newborn calf serum (NCS), in vitro developmental rate of oocytes to the blastocyst stage on Day 9 was not significantly improved compared with that using the base medium for oocyte storage (14.3%, 11.7% and 7.2%, respectively). However, addition of both pyruvate and NCS resulted in a significantly higher blastocyst rate (21.0%) compared with oocytes stored in base medium or with NCS supplementation (ANOVA; P<0.05). Nevertheless, blastocyst development in all stored groups were significantly lower than in the control group fertilized without storage (44.0%). Compared with the control group, oocyte storage significantly reduced the hatching ability of resultant blastocysts with the base medium (73.4% and 31.3%, respectively) but not with pyruvate, NCS or both (54.0%, 56.7% and 46.2, respectively). In conclusion, addition of pyruvate or serum alone did not affect the developmental competence of oocytes during storage. However, simultaneous supplementation with pyruvate and serum had a synergic effect to moderate the reduction of developmental competence during oocyte storage. The study was financed by the NARO Institute of Livestock and Grassland Science, Japan (N32G4126) and the Royal Golden Jubilee-PhD scholarship (2.B.TS/53/F.2).
