Care in AI and Frozen Semen Handling
The quality of frozen semen is determined by the bull and the organization that processed it. Deal only with reputable, well established artificial insemination (AI) organizations. Semen obtained from reputable AI organizations has been processed under standard controlled conditions and is routinely subjected to stringent quality control tests. However, high quality, highly fertile semen can deteriorate rapidly if it is handled or stored carelessly. This guideline contains recommendations for semen tank management, handling semen within the tank, proper thawing procedures, and preparation of the inseminating device.
Frozen bull semen can be stored indefinitely if it is maintained constantly at very low temperatures. The critical temperature is -80o
C. Frozen semen that is exposed to temperatures warmer than -80 o
C (even for a short period of time) and then returned to the tank may be damaged. The extent of damage depends upon how long the semen is exposed to elevated temperatures. Although it is easy to maintain frozen semen at a safe temperature, it is also easy to destroy its quality in a few moments of carelessness.
Handling Semen Before Thawing
In the typical semen tank, dangerously high temperatures exist in the upper half of the neck tube. Semen may be exposed to these temperatures when you try to locate and thaw a specific unit of semen or when you transfer semen from tank to tank. Thermal injury to sperm is permanent and cannot be corrected by returning semen to liquid nitrogen. Semen handling practices important to minimizing thermal damage are:
- Identify which canister contains the desired semen.
- Remove the canister from its storage position to the middle of the tank.
- Grasp the desired rack and immediately lower the canister to the tank floor.
- Immediately after the unit of semen is immersed in water, return the rack to the canister by raising the canister up over the rack. Return the canister to its storage position.
- Any time it takes more than 15 seconds to locate a particular rack, the canister should be lowered back into the tank to cool completely. Never return a unit of semen to the tank once it has been removed from the rack.
- A rule of thumb is to thaw only as many straws as you can use in 10 to 15 minutes. In an emergency situation, a 15 to 20 minute interval between thawing and insemination will not lower semen quality a great deal.
- Avoid thawing more than three straws at once to maintain the correct thaw water temperature.
- After all straws in top goblet have been used, remove the goblet from the cane and clean it for subsequent use.
The recommendation for correct thawing of semen frozen in straws is not the same for all AI organizations. For optimum results the recommendations of the semen processor should be followed. However, almost all processors recommend warm water thawing of straws for 10 to 60 seconds. The problem is that most dairy producers use semen from various AI organizations, and only one thawing procedure is practiced.
- Always keep insemination equipment clean, dry, and warm.
- Use a thermometer; don't guess at the temperature. Check periodically the thermometer for accuracy with a reference thermometer.
- Use an insulated water bath designed for thawing semen wide mouth thermos that is deep enough to immerse the entire straw. Recently, electronic thawing devices have been developed; these maintain water temperature. These are convenient to use when breeding many cows at one time.
- Never thaw more than one unit of semen at a time. You breed cows individually, you should thaw units of semen individually.
- Gently shake the straw as it is taken from the tank to remove any liquid nitrogen that may be retained in the cotton plug end of the straw.
- Time the thaw with a watch to avoid guessing. When possible or practical, use thawing recommendations of the AI organizations from which the semen was processed.
Handling Semen after Thawing and During Insemination
Semen is most frequently damaged during handling after it has been thawed and is being transported to the cow. After thawing, semen temperature must be maintained as close to 35 oC as possible. The handling of thawed semen and preparation of the insemination rod should be in a sheltered area that can be heated in cold weather. The following practices will minimize semen damage that commonly occurs with improper semen handling procedures.
- While the semen is thawing, warm the insemination rod by rubbing it briskly with a paper towel. In cold weather, place the warm rod within clothing so it will be close to your body and maintain its warmth.
- After the semen is thawed for the required time, dry the straw thoroughly with a paper towel and protect it from rapid cooling.
- Adjust the air space in the straw to assure that no semen is lost when the end of the straw is cut off. This can be done by slightly flicking the wrist while holding the straw at the crimp sealed end.
- Transfer the straw to the rod, and cut the tip of the crimp sealed end of the straw through the air space with a pair of sharp scissors. Only sharp scissors or a specially designed straw cutter should be used to cut the straw. Make sure to cut the straw horizontally to achieve a good seal with the sheath.
- Do not place the rod in your mouth or carry it uncovered in your hand.
- Inseminate the cow within minutes after the semen has been thawed. The period of time between removing the semen from the tank and depositing the semen in the cow should not exceed 15 minutes.
Insemination Gun Loading
- Choose a sheltered area for loading the guns and inseminating cattle to help curb undesirable semen temperature fluctuations.
- Before loading the insemination run, warm the barrel if necessary and pull the plunger back about six inches.
- Partially remove a plastic breeding sheath from the container so it is easy to grasp when needed. Make certain no crack exists at the breeding end.
- Remove the straw from the thaw water and wipe it completely dry with a paper towel.
- Check to see that it contains semen from the desired bull and that a small bubble is at the crimped end.
- If the bubble is not at the crimped end, gently tap the straw until the bubble moves to its correct position.
- If you cannot read the printing on the straw, do not use it. Later, ask your semen supplier for a replacement.
- Place the cotton plug end of the straw in the gun. It will stop at exactly the right depth.
- Wipe the scissors with a paper towel and cut off the strap 1/4" below the lab seal. Make a right angle cut to the straw.
- Slide the plastic sheath over the straw and gun. Be sure the white plastic ring is half way on the gun. If it is not, it may become tight before the sheath is all the way on the gun.
- Firmly tighten the white ring with a twisting motion.