485. Modelling of Direct-Transfer Vitrification of Bovine Embryos

Development of an effective direct transfer vitrification procedure for biopsied in vitro derived embryos is necessary for large scale use in the field and increased genetic gain in the cattle industry. One possible reason for insufficient results to date may be the swelling of embryos following warming/transfer. We used mathematical modelling of the volume changes of embryos during and following vitrification protocols, to study the effect of different temperatures and concentrations of cryoprotective agents (CPAs) and non-permeant solutes. The simulations showed no effect of temperature on the level of post-warming swelling at the assumed parameterizations. However, adapted vitrification media with lower concentrations of CPAs and higher non-permeant solutes led to clearly lower swelling after direct transfer, and could potentially be less toxic for the embryos, but also led to a stronger shrinking during vitrification. The alternative media and protocol seem promising, but empirical experiments are needed to validate this approach.