Cattle Today

Cattle Today



by: Mel DeJarnette
Select Sires Reproductive Specialist

When was the last time you stopped to think about the dollar value of the semen inventory in your liquid nitrogen refrigerator? You might be surprised at the final tally.

Although semen costs are only a small percentage of overall expenses in a dairy or beef cattle operation, the absolute value of your semen inventory at any given time may represent a significant sum of money. Proper tank management is essential to keep your investment secure.

Tank Anatomy

Although it does contain other insulation materials, the primary insulating component of a nitrogen refrigerator is the vacuum between the inner and outer tank walls. Once this vacuum is lost, nitrogen will boil away rapidly and render the tank useless.

The inner tank is only connected to the outer shell via the fiberglass neck tube. Fiberglass, being a poor conductor of heat, minimizes temperature transfer from the outside to the inner storage area, thus maximizing the holding time or interval between fills.

Tank Storage

Store your tank in an office or other relatively clean area where it can be easily observed, on a daily basis, if possible. Place your tank on a dry wooden pallet or board.

Avoid direct contact with cement or cleaning compounds commonly found in the milkhouse or parlors. Acids released from sweating cement or strong cleaning agents can cause tank corrosion and lead to failure of the vacuum seal.

The storage area should be well ventilated as nitrogen can displace oxygen in the air. However, drafty areas should be avoided. Increased air movement around the tank opening will increase nitrogen consumption and reduce holding time.

Tank Handling

Avoid moving or transporting your tank more than is absolutely necessary.

When you do have to move it, use common sense. Grasp the tank by both handles to maintain its upright orientation. Handle it gently to avoid undue stress on the neck tube. When transporting a tank in a vehicle, position it on a rubber mat or cushion to help absorb road shock And, strap it down snug and secure.

Tank Management

Increased nitrogen consumption rate is an early sign that your tank is losing its vacuum. Check your tank daily for signs of frosting and once every other week for nitrogen consumption rate.

Work out a collaborative plan with your neighbor to provide each other temporary storage space should a tank emergency develop.

Exposing frozen semen to warm air temperatures and then re cooling damages many sperm cells and reduces potential fertility. Keep canisters as low as possible in the neck tube while removing straws for thawing.

A well lighted area will help you to read bull numbers on the cane tops, thus facilitating this process. Also, an updated semen inventory card will help to avoid exposure by allowing you to go directly to the appropriate canister without having to search the entire inventory.

Using A Dry Shipper

You may at some time receive semen that is shipped to you in a "dry shipper" tank. They are known as dry shippers because they don't usually have liquid nitrogen sloshing around in the bottom of the tank.

Instead, an absorbent material lines the inside wall. This material absorbs liquid nitrogen like a sponge and keeps the semen at the low temperatures required. This type of tank allows shipping weights to be reduced and keeps nitrogen from escaping as quickly if the tank is tipped over during shipping.

Since total storage time is very limited in a dry shipper, you should transfer semen into your regular storage tank as soon as possible after you receive it. This way you can avoid the risk of semen warming up and being damaged. The shipper can then be returned to its owner as quickly as possible.

How Long Does a Semen Tank Last?

With proper maintenance and careful handling, a semen tank should easily last for 10 years or more. In fact, there are many tanks still in service after 20 or more years. However, most of these tanks are much less efficient at holding nitrogen than today's newer models and must be filled on a more frequent basis.

Eventually, all tanks lose their vacuum and are rendered useless. This may occur gradually over time or can occur quite suddenly overnight. The older the tank, the greater the likelihood that its number will soon be up. If you have an old tank (10 years) consider upgrading to a newer, more efficient model.

The dollars spent on a new tank is basically cheap insurance to keep your sometimes sizeable inventory investment secure.


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