There is a common misconception that one semen type is better than others however, it can often be a combination of several factors, which contribute to a successful pregnancy. The type of semen you choose is only one.
Fresh semen
Fresh semen is collected from the stallion and inseminated into the mare very shortly after collection, therefore the mare and stallion are required to be on the same site or very close by. In terms of processing, there is little involved, and your mare’s chance of conceiving are highest when using fresh semen, which is why it is generally recommended for sub-fertile or “tricky” mares.
Fresh Semen - Pros
- Minimal or no semen processing involved
- Less frequent checks by your veterinarian can make this a cheaper option
- Fresh semen has the highest fertility results
Fresh Semen - Cons
- The stallion may not be available
- The semen has a short life span once collected and quality is constantly falling before insemination
- Mare and stallion need to be at the same location or very close by
Chilled semen
Chilled semen is collected from the stallion, a protein-based extender is then added to the sample and the semen processed and chilled before dispatch. Generally, chilled semen is shipped overnight for delivery the following morning, however there are some stallions whose semen must be sent on a Same Day courier service. This is more about longevity than an issue with quality.
Chilled Semen - Pros
- The next best thing to fresh semen, in terms of quality and fertility (although it is becoming more apparent that comparable results can be achieved with chilled and frozen semen)
- Mare and stallion do not need to be at the same location
- The semen can usually travel for 24 hours whilst maintaining good motility, if processed correctly
Tip: Ask the collection centre if they centrifuge the semen sample prior to shipping - Most chilled semen (from around 85% of stallions) will benefit from being centrifuged in order to improve its longevity for travelling
Chilled Semen - Cons
- The stallion may not be available due to training or competition commitments
- There is a chance that the courier may be delayed and not be able to deliver within the 24-hour window
- Timing – the mare may ovulate before the semen arrives
- Shipping fees will apply
Fresh/Chilled Semen FAQ’s
- What is the total concentration of sperm cells in a dose of fresh semen?
World Breeding Federation for Sport Horses (WBFSH) recommend a minimum of 300 million progressively motile sperm cells per dose. Stallion AI Services process fresh semen at a total concentration of 500 million progressively motile sperm cells per dose.
- What should the total concentration of sperm cells be in a dose of chilled semen?
WBFSH recommend a minimum of 600 million progressively motile sperm cells per dose. Stallion AI Services process chilled semen at a total concentration of 1,000 million progressively motile sperm cells per dose.
- What is progressive motility?
A progressively motile sperm swims forward in an essentially straight line, whereas a non-progressively motile sperm swims, but with an abnormal path, such as in tight circles.
- When ordering fresh/chilled semen what progressive motility should I expect to receive?
Progressive motility can vary widely from stallion to stallion, but you should expect to receive a minimum of 35%, with the average being between 50—65%. This applies to both fresh and chilled semen.
- Why does this stallion’s semen need to be sent on a Same Day service?
Occasionally, the semen from some stallions does not tolerate the chilling process which in turn affects the longevity of the semen. This does not necessarily mean that the stallion’s semen quality is poor or that fertility will be reduced, just that using the semen within its capabilities is advised in order to achieve the best possible results. Stallion AI Services will occasionally make the decision to ship Same Day with the mare owner’s best interests in mind, paying a little more for carriage may save you a lot of money in the long run if cycles have to be repeated when your mare is not in foal!
Frozen semen
Frozen semen has been processed, a protein-based extender is then added to the sample and then frozen and stored at -196*C. Stallion AI Services freeze semen at 6 straws per dose, however the number of straws per dose can vary depending on the centre. Frozen semen is considered to be less preferable than fresh and chilled semen, however due to advances in technology, the gap between fresh/chilled and frozen is shrinking and in fact, frozen semen from some stallions achieves better conception rates than their chilled semen.
Frozen Semen - Pros
- Once frozen, the semen can last indefinitely provided it is stored correctly
- The straws can be ordered in advance of your mare being ready for insemination
- Frozen semen can travel further than fresh and chilled semen. The shipping flasks can last anywhere from 7 -21 days, which means the semen can travel worldwide providing that it qualifies for export to that country
- Stallion’s availability is not a problem
Frozen Semen - Cons
- Once thawed and inseminated, frozen semen has a shorter life span inside the mare (approx. 6 hours), which means insemination must be as close to ovulation as possible this increases the frequency of veterinary scans required
- More frequent checks by your veterinarian can make frozen AI more expensive
- Not all veterinarians are well practiced in handling, thawing and inseminating frozen semen, it is important to use an experienced veterinarian
- The semen must be stored in liquid nitrogen (-196 degrees) before use.
- Some veterinary practices do not have storage facilities, this is important to check prior to ordering the semen
Frozen Semen FAQ’s
- How long does frozen semen last? Does it have an expiry date?
Indefinitely, when stored and maintained correctly in liquid nitrogen. The frozen semen should be at a temperature of -196 degrees whilst stored. Stallion AI Services would recommend the semen is handled by an experienced laboratory technician or veterinarian
- What is a dose?
A dose is made up from a number of straws (usually between 1-8 straws) and has been calculated to contain the optimum concentration of sperm cells in order to achieve a pregnancy, which Breeding Federation for Sport Horses (WBFSH) recommend at 250 million progressively motile sperm cells per insemination. Stallion AI Services freeze semen at 300 million PMS per insemination.
- When ordering frozen semen, what progressive motility should I expect to receive?
You should expect to receive a minimum post thaw motility of 35%, with the average being between 35—45%.
It is important to ask the following questions when purchasing frozen semen to enable you to make sure you’re getting the optimum insemination dose to give you the best chance of achieving a pregnancy:
- What’s the concentration i.e. how many million sperm cells per ml?
- How many straws am I getting?
- What is the post thaw progressive motility of the semen?
*REMEMBER THE MAGIC NUMBER*
- 250 million progressively motile sperm (PMS) cells per insemination
Example Calculation:
250 million per ml (remember straws are 0.5ml so this would need dividing by 2)
- 6 x 0.5ml straws
- 35% Progressively motile (PMS)
- Total concentration per ml (250) ÷ Straw Volume (2) = Concentration Per Straw (125)
- Concentration Per Straw (125) × Percentage of PMS (35%) = Number PMS per straw (43.75)
- Final insemination PMS (The Magic Number 250 million) ÷ Number PMS per straw (43.75) = Number of straws needed per insemination 5.71 (6)
So, in this example, are you getting back to “the magic number”?
- Yes, you’re getting 262.5 million PMS cells.
There are occasions where the number of straws per dose has been reduced from what it was originally frozen at, for example, when a stallion has subsequently died, and the stock of frozen semen is limited, or the pregnancy rates have been excellent. In this instance and when purchasing semen by the straw, it is important to factor in pregnancy data for each stallion as this can help you determine the optimum insemination dose. An exception to this rule is when the fertility of the semen is known – There are top stallions whose semen is achieving exceptional conception rates with less than 250 million PMS per insemination.
When purchasing semen by the straw via Stallion AI Services, the optimal insemination dose is always clearly outlined in our stud terms for each stallion.
Expertise and experience are both essential to give you every chance of achieving a pregnancy with your mare, where there are so many variables. By choosing a stallion whose semen is collected and processed by Stallion AI Services, you can have confidence that from the care of the stallion to the shipping of the semen, every detail has been considered and the semen you will receive will be of the best quality achievable for each individual stallion
