The young embryos can be frozen and stored in liquid nitrogen for up to 10 years or more and used a subsequent date. The frozen embryos are far easier to transport and present negligible quarantine problems as compared to the animals themselves.
The embryos are first treated with a suitable concentration of a compound like glycerol which protects them from injury during freezing and thawing and such compounds are called Cryoprotecteats. They are then cooled at a slow rate to -38o C, ordinarily employing a programmable controlled rate freeze. These embryos are then plunged into liquid nitrogen and stored at -196o C. the embryos are thawed at a very rapid rate by immersing the ampoule carrying them into a water bath maintained at 0oC.