Open Pulled Straw (OPS) vitrification of porcine blastocysts: Simple procedure yielding excellent in vitro survival, but so far no piglets following transfer

In 2 trials, 346 porcine in vivo blastocysts were vitrified in heat-softene d and pulled French straws by the Open Pulled Straw (OPS) vitrification met hod. After thawing, embryos were either cultured in vitro (n=89) for 24 to 48 hours or transferred surgically (n=257) to 11 synchronised recipients wi thout further culture. In trial 1, 88% and 71% of thawed blastocysts reexpa nded and hatched in vitro, respectively, while 71% reexpanded in trial 2. H owever, no piglets were born following transfer, though I recipient was dia gnosed pregnant at Day 56 of gestation.