By Sandy Johnson, Extension Beef Specialist, Colby
Many factors influence the success of an artificial insemination (AI) program. The male component of the fertility equation can often be overlooked. What was once the highest quality semen can become worthless if improper handling occurs any time before insemination.
Liquid nitrogen (LN) is used to store semen at a temperature of -320 °F. Depending on the level of LN in the tank, there is a temperature gradient in the neck of the tank, ranging from about -292 to -313 °F to +36 to +54 °F at the top. Sperm injury occurs at -100 °F, so even when the straw is still frozen, damage can occur. Repeatedly allowing canes to warm to this degree compounds problems because the injury is not corrected when the canister is lowered again. In this case the last straw in the cane is at most risk. Semen packaged in ¼ cc straws are more sensitive to mishandling as the smaller diameter allows them to warm more quickly.
The following are best management practices for managing liquid nitrogen tanks and handling semen
- Develop and maintain a semen inventory system so straws can be located rapidly.
- Store tank in a dry, well-ventilated area, out of heat and direct sunlight.
- Don’t set tank directly on a cement floor, drag it across any floor, drop or bang into solid objects
- Monitor liquid nitrogen level regularly as appropriate for the tank holding time, maintain at least 6 inches of liquid nitrogen
- Keep canisters below the frostline when locating semen. Drop canister back down into tank if elevated for more than 5-10 seconds. If you see vapor or hear LN boiling when you lower the canister, it has been elevated more than 10 seconds
- Use of long-nosed tweezers to extract straws helps keep work below the frostline.
- Keep interior of thaw unit clean
- Test temperature of thaw unit regularly, target range is 95-98°F
- Keep thaw water clean, change at least daily or more often as needed
- Use cold water to refill thaw unit to avoid over heating
- Do not allow straws to touch in thaw bath
- Thaw straws for 45 seconds and do not thaw more semen than can be used in 10-15 minutes
- Keep insemination gun and scissors (or cito cutter) cleaned and disinfected
- Dry straw before cutting, water is deadly to sperm cells
- Make every effort to maintain straw temperature in-between removing straw from thaw water and reaching the female to inseminate.
Remember that LN can cause serious burns. Use gloves and safety glasses to prevent burns and injury from exploding straws. Follow these guidelines emphasizing time, temperature, cleanliness, and good technique to help maximize the semen component of fertility in your AI program.