As calving season winds down and cow-calf pairs head off to pasture, it’s time to turn our attention to breeding season. You probably spent some time studying AI sires, their EPDs, price, and confirmation, but none of that matters if your semen tank isn’t doing its job.
Semen tank maintenance is a small piece of farm management that may be overlooked, but once something goes wrong, you’ll be paying the price. Semen is a significant investment on your farm and proper maintenance and care of your tank will protect that investment. A properly maintained tank will safely store semen for years, sometimes decades.
The standard temperature inside a liquid nitrogen tank is -320 °F. The body of the tank is where all unused semen should remain as much as possible. The neck of the tank rapidly warms closer to the opening at the top. A tank with a six inch neck ranges from -320 °F in the body of the tank to around -103 °F at the frost line (base of the tank neck) to above zero at the opening. When removing a straw, it is important to keep the canister and straw you are working with as low in the tank as possible. Work quickly and carefully. Never completely remove a straw or canister from a tank, this will likely result in sperm damage. Sperm damage can occur at -112 °F, which is why it is critical to keep straws and canisters below the frost line. In addition, rapid warming and cooling of straws by taking them out of the tank and returning them causes recrystallization. Large ice crystals damage sperm cells membranes and organelles. Damaged sperm cells will result in lowered motility.
Maintaining your tank’s integrity is a critical piece of management that should not be ignored. First and foremost, monitoring liquid nitrogen levels is key. Recommendations for minimum liquid nitrogen levels in a tank are 3-6 inches. Never let your tank fall below that level, and if your tank level is low, check it frequently until you can get a refill. Low liquid nitrogen levels could indicate your tank is leaking.
Store your tank in a place where it doesn’t have to be moved or jostled around. The less you move a tank, the better it will maintain integrity. Store your tank on a pallet or off the floor if possible so corrosive materials do not come in contact with it. Be sure the room is well-ventilated and depending on your farm situation, the room (or the tank) may need to be locked. Monitor your cork/cap of the tank. This one relatively inexpensive part can save you a lot of money if damage or loss of integrity is detected early. Inspect the cork when you use the tank, a shiny cork should be replaced as soon as possible. Frost buildup around the neck of the tank indicates a loss of vacuum. Even new tanks can have defects that cause leaks. A compromised tank will lose liquid nitrogen very quickly, so it’s a good idea to check your tank on a schedule, especially in the off season when it isn’t used often. Leaking liquid nitrogen doesn’t last long around the tank, so keeping your tank clean and in a well-lit area can help you see frosting when checking for damage. A well-sealed and properly functioning tank will not develop frost on the outside.
Maintaining your semen tank protects your farm investment. Make semen tank maintenance part of your management protocols on the farm and you’ll be sure to save yourself unexpected surprises at breeding season.
Written by: Aerica Bjurstrom, UW-Madison Division of Extension Kewaunee County, and recently appeared in Wisconsin Cattlemen’s Cattle Trails Newsletter