Veterinarian View
Health & Reproduction questions answered and explained.
contributed article by Dr. Vince Collison, Collison Embryo | Collison Veterinary Services, Rockwell City, IA collisonembryo.com
EMBRYO & SEMEN HANDLING BASICS O
ne thing that makes me cringe is seeing an owner pulling canes way out of the neck of a nitrogen tank to look to see what it is prior to transfer or AI. The first key to good results with frozen embryos or semen is to keep them frozen until the time you are ready to thaw them. When an embryo is cryopreserved, it has to remain in the frozen state at all times to maintain integrity. Some of the numbers to remember for handling frozen embryos and semen are these:
1) -196 DEGREES CELSIUS This is the temperature of liquid nitrogen. This is the temperature where all metab-
olism stops on cells and any intracellular ice crystals are stable. This is also the temperature of the body of a liquid nitrogen tank where all the goblets are stored. A tank can get to a fairly low level of liquid nitrogen and still maintain this temperature in the body of the tank.
2) -130 DEGREES CELSIUS This is the highest temperature where ice crystals within the cryopreserved cells stay stable. If temperatures go above this level on frozen embryos or semen, there will be recrystallization of ice crystals inside of the cells. This recrystallization process causes shearing of cell membranes resulting in irreversible
damage. The straws in this case can be warmed up above this level and damage occurs without ever being totally thawed.
3) -80 DEGREES CELSIUS This is the temperature in the neck of the nitrogen tank. The other thing to be aware of is a ¼ cc straw is more prone to thaw damage than a ½ cc straw since the surface area relative to the volume is higher in the ¼ cc straw. As semen becomes more commonly packaged in ¼ cc straws it will be more important to handle semen correctly for best results. Also all embryos are packaged in ¼ cc straws, so they are at higher risk for thawing. For people that store their own embryos we recommend these guidelines:
August 2020
1) Keep the nitrogen tanks at least 50% full at all times. This will keep the lower goblet submerged in nitrogen and also help reduce the risk if you pull the canister up into the neck of the tank.
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