An AI flask is insulated to store liquid nitrogen, which is used to keep AI straws frozen at -196°C. As an AI flask ages, it loses some of its insulative capacity. As a result, the liquid nitrogen may be lost at a faster rate. Usually AI flasks are topped up every three months or four times per year.

Tanks should be stored in a cool, dry place out of direct sunlight. Ideally, place the AI flask on a timber board or pallet and not on a wet concrete floor. The nitrogen level should be checked at regular intervals to avoid it running dry.

Handling straws

Semen is sensitive to temperature changes. Straws should be kept submerged in liquid nitrogen at all times if possible. It is advisable to always use tweezers for handling straws. Picking them up with your fingers will allow heat to travel to the straw, which could potentially be damaging to the semen in the straw.

To reduce the amount of handling required when searching for straws in an AI flask, it is beneficial to have a diagram showing where straws are in the flask. When removing the AI straw from the flask, this should be done within 10 seconds of the canister being raised into the neck of the flask to avoid thermal damage to the semen. If it takes more than 8 seconds to locate an AI straw in the canister, then the canister should be dropped back down into the liquid nitrogen to cool for a period of 30 seconds before lifting again.

Thawing straws

Once the goblet is lifted to within 1-2 inches of the top of the neck of the flask, the required straw should be removed with a tweezers within 10 seconds, the goblet should be lowered back into the flask and the lid put in place. Shake the straw to ensure all liquid nitrogen is removed.

The straw should then be placed in a thawing flask with the water at 33-36°C. It will take 50-60 seconds for the straw to thaw fully. Check the temperature of the water using a thermometer before thawing the straw.

Loading the straw

Once the straw is removed from the thawing flask, it should be dried using a paper towel as semen can be killed by contact with water. It is advisable, particularly in cold weather, to warm the AI gun while keeping it dry in order to avoid the temperature of the straw dropping before the cow is served.

The semen should ideally be placed in the cow within five minutes of thawing. The straw needs to be kept between 33-36°C between loading and insemination. In cold weather, ensure that the straw does not drop in temperature during this period.

Hygiene at insemination

Hygiene is critical at AI. When removing a sheath from the pack, only touch the bottom end of it. Sheath covers which are thin plastic films can be used to cover the sheath and keep the sheath clean as it enters the cow.

Once you have started to insert the AI gun you can push the sheath through the end of the sheath cover. This will ensure no dirt enters the cows cervix at insemination.