A new technique will be developed for the rapid freezing of bovine embryos in late morula stage. The approach is based on the fact that each embryo is a developing system whose response to freezing is unique. The proposed method quantitatively assesses the state of development for each embryo and formulates an optimum freezing protocol for that embryo. No penetrating cryoprotectant is employed and the process is nearly completely automated. This simplified technique assures that only viable embryos are frozen, thawed, and transferred. The research will include transfer of embryos frozen and thawed by this new technique to surrogate female cows and/or heifers. Pregnancy rates from the new methcd are exp cted to be substantially in excess of rates currently possible with either frozen or on-frozen embryos.
