Semen Freezing and Storage

Preserving your stallion genetics is key and we offer this procedure in our equine reproduction laboratory at Luskintyre.


 Increased quality control:

  • The use of frozen semen allows pre-screening for infectious diseases and a thorough evaluation of the semen quality after collection and after thawing. This allows owners to be informed about the quality of the frozen semen available and be more realistic about what to expect in pregnancy rates when used.
  • National and global market of your stallion’s bloodline:
    • Semen can be frozen, shipped far in advance (in contrast with fresh and cooled semen) and stored on premises for a long time (frozen semen can be kept for an infinite period of time if properly stored!) until the mare is ready for insemination.
  • Protect your stallion’s genetics:
    • Under any unexpected circumstance (taking out of breeding, injured, severely ill, sold or death) you have insured your future by freezing that genetic potential and you will have a back-up plan. Remember that the best time to freeze semen from a stallion is when he is young and healthy.
  • Preserve semen prior to gelding
    • Your stallion might; have behavioural issues which you hope to control through gelding, need to focus on his career, not have the mindset for the dual role (breeding and competing), or you have a barn management concern with having a stallion on the property. Freezing your stallion’s semen prior to a scheduled gelding gives you an opportunity to look after your best interests and have your stallion’s future ensured.
  • To save money: frozen semen is more cost effective for both mare owners and stallions:
    • The cost of shipping frozen semen is far more cost efficient than shipping a mare or a stallion. Frozen semen improves convenience to the mare owner by increasing your stallion availability and desirability.
  • To increase the volume of breedings for your stallion
    • Frozen semen removes all inconvenient associated with semen requests during show season or when logistically inconvenient (mares become ready on her own time, and often that time is inconvenient!).
    • Semen can be frozen all year round increasing the number of breeding doses available for your stallion during a “non busy” time of the year


Not all stallions have semen which freezes well:

  • There is an individual variation amongst stallions that undergoes freezing. This means that until your stallion’s semen is frozen and evaluated after thawing, you don’t know if he would undergo the process satisfactorily. The industry standard for commercial distribution of semen is >30% post-thaw progressive motility. Approximately 25% of stallions freeze well, 50% freeze fairly well, and 25% freeze poorly.

Not all mares are good candidates for breeding with frozen semen

  • When breeding mares with frozen semen it is best to choose young, reproductively sound mares. In older and problem mares, pregnancy rates after insemination with frozen semen are lower than AI with fresh semen.


  • First, your stallion should be collected regularly, or, alternatively, have a number of “clean-out” collections to release the lengthy stored sperm cells and increase the proportion of newly produced sperm cells in the ejaculation that will undergo the freezing process. Stallion production of sperm is constant and, if not released regularly (by semen collection or mating), sperm cells “age” and are less able to withstand the rigors of the freezing process.
  • After cleaning out your stallion, regular (commonly 3 times a week) semen collections are performed out of a “phantom mare” or “dummy” using an artificial vagina.
  • Semen obtained will be centrifuged to concentrate it and remove the seminal plasma, followed by re-extension in a freezing extender (specifically formulated). This extender contains cryoprotectants (one of several types available) that protect the sperm cells from the severe stress that occurs as they undergo a significant decrease in temperature (freezing process).
  • The extended semen is then loaded in straws (0.5ml) at standard concentration to meet the current industry standards.
  • Loaded semen straws sit over liquid nitrogen vapours to slowly decrease the temperature, after which they are placed in the liquid nitrogen and stored for an infinite time, as needed.
  • Post-thaw evaluation: one semen straw is thawed after being 24hs frozen and is evaluated on the microscope to determine its progressive motility. This evaluation allows to determine the number of straws that will made up a breeding dose (the number of straws needed to breed one mare) and depends on each individual stallion’s post-thaw motility and the specific freezing protocol used. Each breeding dose should contain > 250 million progressively motile sperm cells after thawing to optimize fertility, commonly contained in between 4 to 8 semen straws (0.5ml). Artificial insemination is performed just before/immediately after ovulation and requires sterile technique.

While the process of freezing stallion semen sounds simple, there are a huge variety of factors involved in obtaining frozen semen of good quality.

If you are thinking on freezing and conserving semen from your stallion, make sure to contact us and have our experience equine reproductive specialist Dr. Agustin leading you and your stallion to success.