ONE OF the major components of fertility in dairy cows is the management of the artificial insemination (AI) program. There is no single 'silver bullet' to achieving good pregnancy rates - it is all about attention to detail for several things.
This article focuses on the AI technique.
Good semen handling vital Only buy semen from reputable service providers. Collecting and processing semen is a highly technical skill and farmers really want to be confident that the person or company doing it is appropriately qualified.
Once the semen is delivered to the AI tank at the farm, make sure liquid nitrogen levels are measured weekly with a measuring stick. Never allow the liquid level to fall below 10 centimetres before getting a top up. On average, most farm tanks will need topping up with liquid nitrogen every six to eight weeks during AI season.
When removing straws from the tank, always hold the canister at the level of the frost-line, which is about half way down the neck of the tank. This means tweezers or forceps need to be used to remove the semen straws from the tank.
Too many AI technicians are in general too casual about this and are damaging the semen by lifting the canisters too high in the tank. Each time a canister is lifted, the straws begin to thaw within two seconds, so be mindful of the damage being done to the straws that remain in the canister. Repeated exposure to temperature change in this way is harmful to semen.
Thaw semen in warm water Frozen bovine semen should be thawed in water that is between 32 and 38 degrees Celsius.
It is important to have a thermometer that actually works and use it. Automatic thawing flasks available that are plugged in to keep the water at a correct temperature and these are terrific.
There are still a few people out there who ignore the science and don't use warm water for thawing and just jam the straw in their pocket or wave it about in the air for a brief few seconds. This is the sign of a careless inseminator. That straw of semen has been scientifically processed and it is important that the science is continued to be applied right until the semen is inside the cow. The manufacturers all recommend that frozen semen is thawed in warm water and these instructions are there for a good reason.
Sexed semen straws are especially vulnerable to mishandling and should always be thawed in water that is 35 degrees Celsius.
On cold days, it is advisable to warm the barrel of the AI gun by rubbing it in the hand before inserting the thawed semen straw, and once loaded, it is a good thing to store the loaded AI gun in a gun warmer or down the front of the shirt wrapped in a piece of paper towel to protect the end from contamination.
It takes about 20 seconds for the temperature of the semen in a loaded AI gun to drop to the ambient temperature thereby starting to damage the sperm cells so it is important to protect loaded guns on cold days.
The more live, viable sperm that reach the cow's oocyte then the greater the chances of fertilisation taking place so it stands to reason that semen should be thawed and handled correctly to get the highest number of sperm in the right place at the right time.
Don't neglect heat detection Many people don't understand why it is so important to do a good job with heat detection.
The onset of standing heat in a cow is the most reliable sign that ovulation is going to occur 24-30 hours later. Once a cow ovulates and its egg is released, the egg will remain viable for about six to eight hours and this is the window when conception has to take place. So if a viable number of good quality sperm are not in the reproductive tract at the time that coincides with the release of the egg, then conception becomes highly unlikely.
Semen will last inside the cow's reproductive tract for about 24 hours.
Heat detection is important because it is the link to knowing when the cow will ovulate.
Deposit semen in the uterus All the semen should be deposited into the body of the uterus.
This may be a different recommendation to any person who did their AI training before 2000. In those earlier days, people were told to deposit two-thirds in the uterus and one-third in the cervix. However, this is no longer regarded as best practice and many scientific studies have reinforced the recommendation that fertility increases if all of the semen is deposited into the uterus.
It is important, however, that the semen is deposited in the body of the uterus and not up one of the horns of the uterus as there is a danger that the cow has cycled on the opposite ovary.
If these simple aspects of AI technique are kept in mind, there is a greater chance of a good population of viable sperm being in the correct place at the correct time so that conception will take place.
There are no 'silver bullets' - just pay attention to detail and don't take any shortcuts because there are none if aiming to maximise pregnancy rates.