Embryo Cryopreservation

Precise, Science based protocols

Cryopreservation in reproductive medicine is an artificial means of ‘stopping the biological clock’ enabling the preservation of genetic material through cooling and ultimately suspending the embryos at ultra-low temperatures (-196°C) in liquid nitrogen to preserve them for future use. To date, two strategies have dominated the field of cryopreservation; slow freezing and vitrification.

Slow freezing, including direct transfer (DT), requires embryos to be dehydrated with the aid of cryoprotectants. Then a controlled rate, programmable freezer allows the embryos to be cooled slowly (~0.5°C/min) to around -32°C. Following cooling, embryos are ‘plunged’ into liquid nitrogen at -196°C for long term storage.
Vitrification preserves embryos by a rapid initial dehydration followed by a direct plunge into liquid nitrogen. It comes from the Latin phrase “glass,” and is defined as the process of transforming a water-based solution into a solid glass-like state in the absence of ice crystals. During vitrification, the risk of chilling injury is greatly reduced, and the cell viability is increase due to the absence of ice crystals.

Why Choose Embryo Cryopreservation?

Allows for the embryos to be selected and frozen at their ideal stage to match future recipient synchrony.
Short or long-term storage of high-quality embryos – which allows for flexible timing for transfer to recipient cows.
Allows for “embryo banking”, where multiple embryos can be frozen from different OPU programs, and transfer into recipients all in the same ET program
Cryopreservation allows for the preservation of elite genetics.
Frozen embryos can be shipped safely.
It provides a back up supply for fresh embryo programs.

Why is Embryo Cryopreservation important?

Embryo cryopreservation ensures long-term flexibility and security in breeding programs. At Evogene, all frozen embryos are carefully washed, labelled, and stored in liquid nitrogen vessels in full compliance with IETS standards—guaranteeing safety, traceability, and peace of mind. Every stage of the freezing and warming process is managed with precision, protecting embryo viability and supporting the best possible pregnancy outcomes in each production system.

Are fresh embryos better than frozen?

With Evogene, there is no difference. Our laboratory average over the past 5 years including all breeds and all programs is 59% for both fresh and frozen embryos.

How can embryos be frozen?

Embryos can be cryopreserved using two main techniques, each designed to maintain their viability for future use:

1. Vitrification (Ultra-Rapid Freezing)
  - Embryos are exposed to a high concentration of cryoprotectants and frozen extremely quickly to prevent ice crystal formation, which can damage cells.
  - This method results in a glass-like solid state, maximising survival rates after thawing.
  - Vitrification is widely used for high-value embryos, particularly when long-term storage or transport is required.
2. DT (Direct Transfer) Method
  - Embryos are treated with special cryoprotectants and loading into straws that allow them to be thawed and transferred directly into a recipient without additional manipulation.
  - This method is convenient, reduces handling, and is ideal when technicians are unavailable to warm embryos

How long can embryos be stored?

Embryos can be stored for many years in liquid nitrogen at ultra-low temperatures, effectively halting all biological activity and preserving their viability. With proper storage and monitoring, embryos remain just as healthy and capable of developing into successful pregnancies whether they are used months or even decades later.

Cryopreservation (Embryo Freezing)