When calving season finishes and cow-calf pairs head off to pasture, it’s time to turn attention to the breeding season. Time is spent studying artificial-insemination sires, their expected progeny differences, prices and confirmation. But it’s wasted time if the 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 the farmer will be paying the price. Semen is a significant investment on the farm. Proper maintenance and care of tanks will protect those investments. A properly maintained tank will safely store semen for years, sometimes decades.

The standard temperature inside a liquid-nitrogen tank is negative-320 degrees Fahrenheit. 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 6-inch neck ranges from negative-320 degrees in the body of the tank to about negative-103 degrees at the frost line — the base of the tank neck. It can be more than zero degrees at the opening.

When removing a straw it’s important to keep the canister and straw as low in the tank as possible. Work quickly and carefully. Never completely remove a straw or canister from a tank; that will likely result in sperm damage. Sperm damage can occur at negative-112 degrees, which is why it’s 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 re-crystallization. Large ice crystals damage sperm-cell membranes and organelles. Damaged sperm cells will result in less motility.

Maintaining tank 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 to 6 inches. Never let a tank decrease to less than that level. If a tank level is low, check it frequently until it’s refilled. Low liquid-nitrogen levels could indicate a tank is leaking.
  • Store tanks in a place where they don’t need to be moved or jostled around. The less a tank is moved, the better it will maintain integrity.
  • Store tanks on pallets or off the floor if possible. That’s so corrosive materials
  • don’t come in contact with them.
  • Be sure the room is well-ventilated.
  • Depending on the farm situation, the room — or the tank — may need to be locked.
  • Monitor the cork or cap of the tank. That one relatively inexpensive part can save a lot of money if damage or loss of integrity is detected early. Inspect the cork when using 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 quickly so it’s a good idea to check tanks on a schedule, especially in the off-season when they aren’t used often. Leaking liquid nitrogen doesn’t last long around the tank. So keeping tanks clean and in well-lit areas can help to see frosting when checking for damage. A well-sealed and properly functioning tank will not develop frost on the outside.

Maintaining semen tanks protects farm investments. Make semen-tank maintenance part of management protocols on the farm.

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Aerica Bjurstrom is an agent for the University of Wisconsin-Extension in Kewaunee County. Visit extension.wisc.edu for more information.