Delivering High Quality Semen

Sandy Johnson, extension beef specialist, Colby

High-quality semen is a critical component of artificial insemination (the original AI) programs. Collecting and packaging semen is a routine job performed by highly trained professionals. Once it leaves the collection site, its quality is maintained only through proper handling as it makes its way to the cow. A 20-liter liquid nitrogen (LN) tank can hold up to 720, 0.5 cc straws of semen, making its contents a significant investment.

A LN tank can be thought of as a large thermos with a vacuum between the inner and outer walls. The vacuum must remain intact to maintain the proper storage temperature. If frost is seen on the outside of the tank, action must be taken immediately as the seal has been lost.

Tank management guidelines

• stored in a cool, well-ventilated area, out of direct sunlight, and not in direct contact with concrete
• Avoid dents and scratches, and inspect regularly for signs of wear
• Replace bad stoppers, keep the stopper and dust cover in place to reduce the chance of a frozen stopper.
• Monitor tank LN level on a regular basis

When transporting LN tanks, they should not be in the same vehicle compartment as people. As liquid nitrogen vaporizes, it displaces oxygen. A study by ABS Global placed 2 newly filled LN tanks in a crew cab pickup, and within 3 minutes, the oxygen level in the cab was unsafe for people.

There is a temperature gradient in the neck of the tank. The temperature below the frost line can range from -40 to -120 °C, depending on the tank model and the level of LN in the tank. Damage to sperm cells can occur at temperatures as low as -80 °C. Once the damage occurs, it is permanent.

Items that decrease the risk of handling damage include

• Tank inventory system
• Have the tank filled near the start of the breeding season
• Ensure the semen handler can see the print on top of canes (are bifocals or a light needed?).
• Avoid multiple sires in the same canister with similar codes
• Use tweezers rather than fingers to pull straws – touching more than one straw can raise the temperature of adjacent straws, and larger fingers may force the cane to be raised higher in the neck
• Work below the frost line and lower the canister if the straw cannot be removed within 8 seconds. If vapors appear when you lower the canister, you have held it too high for over 10 seconds.

When thawing semen

• Check thaw bath temperature before starting and regularly (95-98°F) during use
• Thaw for 30 to 60 seconds based on provider recommendations.
• Only thaw as many straws as you can inseminate in 15 minutes
• Do not let straws touch while thawing multiples
• Load straw into a warm gun and maintain warmth

We often focus on factors that might impact cow fertility when evaluating an AI program. Just as important is the male contribution. Review your process to ensure that semen quality does not limit the outcome.