Embryo vitrification (freezing) can be performed on site at HERC. The process involves breeding the donor mare and timing her flush in order to obtain a 6 day old embryo (morula). The embryo is then processed and frozen in liquid nitrogen where it can be stored, indefinitely.  Standard embryo transfer practices allow for 6-8 day embryos to be moved from the donor to the recipient mare, making the timing of flush day with respect to ovulation slightly more lenient.  However, only 6 day old embryos survive vitrification, making the timing of the transfer more difficult. Transfer success is also typically lower in vitrified embryos.  For these reasons, vitrification is not suggested if traditional embryo transfer is an option.