Advanced in vitro production of pig blastocysts obtained through determining the time for glucose supplementation.

The objective was to determine the effect of glucose supplementation on development (to the blastocyst stage) of in vitro matured (IVM) porcine oocytes that were either in vitro fertilized (IVF) or electrically activated (EA). Embryos were incubated for 46 or 58 h post insemination (hpi) in an NCSU37-based medium containing 0.17 mM sodium pyruvate and 2.73 mM sodium lactate (IVC-PyrLac), and then transferred to an NCSU37-based medium containing 5.55 mM glucose (IVC-Glu) and cultured until Days 6 (Day 0 = day of EA or IVF). The proportions of oocytes that had formed full blastocysts by Day 6 following transfer to IVC-glu at 46 hpi was 23.5 and 41.2% in the IVF and EA groups respectively; these were lower (P<0.001) than the proportions of oocytes that formed full blastocysts after transfer at 58 hpi (60.3 and 78.7%). However, there was no significant difference in total cell number (at Day 6) between embryos transferred at 46 vs 58 hpi. We inferred that in vitro-derived pig embryos can efficiently use glucose as an energy source starting at approximately 58 hpi; exposure to glucose at that time enhanced development to the blastocyst stage as well as blastocyst quality.