Fresh Embryo Transfer
Following surgical flush or IVF culture, each embryo is microscopically evaluated to determine if it is viable. Viable embryos are sorted from nonviable embryos and prepared for transfer. A programmed recipient female is sedated, surgically prepped, and the ovaries are laparoscopically examined for functional corpus luteums (CL) laparoscopically. The CL indicates which ovary has ovulated and the quality of that ovulation. If an adequate CL is present, the technician will then exteriorize the uterine horn on the same side as the ovary with the functional CL. The embryo is gently expelled into the uterine horn, taking great care not to damage the lining of the uterus, which could significantly diminish the likelihood of a successful pregnancy being established. In the absence of a CL or presence of unsuitable CL is observed, the recipient is passed and will not receive an embryo as her uterine environment is not suitable for establishing and maintaining a pregnancy.
Frozen Embryo Transfer
Most small ruminant embryos are frozen for direct thaw (DT) or multi-step thaw using glycerol (GLY). These two methods differ in regard to the agent used to cryopreserve the embryo and steps required to thaw the embryo. For embryos frozen using the DT method, thawing for transfer is a simple process. The straw containing the embryo(s) is removed from the liquid nitrogen tank and allowed to air-thaw for a few seconds prior to being placed in a warm water bath for 15 seconds. The embryo(s) is then unloaded and placed into a holding media awaiting transfer. Glycerol frozen embryos require a multi-step thaw process to allow for a gentle rehydration of the embryo. However the process can take up to 15 minutes for each set. Once both types of embryos are thawed, they will be loaded and transferred into the recipient following the same procedure described above for fresh embryo transfer.