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Frozen Equine Semen Basics

Basic Requirements for Breeding Success

Have you heard that breeding mares with frozen semen is difficult and expensive? Or that conception rates are much lower than with live cover or fresh cooled semen? Or that veterinary costs are higher? Don’t let these and other misconceptions dissuade you from trying the most convenient, cost-effective method of breeding. Frozen semen conception rates are now comparable to those of live cover and fresh cooled, and more stallions than ever are being frozen, making it possible for you to breed to the world’s elite performance horse stallions. As with any breeding method, however, there are techniques for the use of frozen semen that result in optimal success.

By understanding three basic requirements, you will have the best chance for achieving breeding success with frozen semen:

  1. A good mare candidate. Breeding success depends most upon the mare--she is the one who must conceive and carry a foal to delivery. All a stallion can do is provide the sperm to fertilize the egg. After that it’s up to the mare to sustain a pregnancy. A relatively young mare who has a foal on her side, is having her first true heat (as opposed to a foal heat, which has only a 35% or less conception rate), and who had no difficulties foaling, is the best choice. Already a proven producer, she is likely to have a normal cycle, and, because of her youth, usually has good uterine tone and normal hormonal functions. A young maiden mare is also a good choice, providing she has not recently come out of hard training. It often takes such mares a year or more to recover from the stress of hard use and become efficient in cycling. An older mare who has been a reliable producer and has a foal at foot will also often conceive with frozen semen. But, the older a mare gets the less reproductively reliable she becomes. She may have scaring from infections, loss of uterine tone, declining hormone levels and other difficulties. These mares must be evaluated on a case-by-case basis. An older maiden mare, such as a 17 or 18-year-old performance mare at the end of her career, is a dubious choice. This type of mare can be difficult and expensive to get in foal, although some of them do end up conceiving. The worst mare candidate for breeding is any mare 17-years-old or older, who was barren the previous year. Any mare that has proven difficult or failed to get pregnant via live cover or fresh-cooled semen is a bad risk Such mares have a greatly reduced chance of ever getting in foal again, even with live cover breeding. Realize also that, although it’s rare, some mares who are reproductively sound in all respects, and have no apparent problem, will not conceive with frozen semen. Their systems simply "don’t like it." There are also a miniscule number of mares who are alergic to the semen extender and on whom frozen semen cannot be used. Whatever mare you choose to breed, have her in good health and do a pre-breeding reproductive soundness exam. It will be the best money you spend.
  2. An experienced veterinarian. When it comes to artificial insemination with frozen semen, a good veterinarian is one who has had training and experience using it, stays abreast of the latest developments and technologies and is willing to go to the extra work to check your near-to-ovulating mare at regular intervals around-the-clock, to be sure she is inseminated within the proper "window of opportunity." Veterinarians all have their areas of expertise and, if you can, you should use one experienced with artificial insemination using frozen semen. When selecting a veterinarian to do the insemination, ask him or her how many mares they have inseminated with frozen semen, and what their first-cycle conception rate is, as well as their overall rate. The conception rate for frozen semen ranges from 55 to 75% or better. If the conception rate of the person you are interviewing falls well below that, reconsider your choice. If they don’t have as much experience as you’d like, but you feel comfortable using them anyway, go for it. It’s a skill that can be quickly mastered by an interested veterinarian willing to bring him or herself up-to-speed on the latest information and techniques. As long as they are willing to check the mare frequently and inseminate at the proper time, they have a good chance of success.
  3. Quality semen. High quality semen known for getting mares in foal, purchased from a reputable semen broker offers the best chance of conception. When you inquire about a stallion’s semen you should ask:
  • How many straws are in a dose?
  • How many sperm are in a dose? Six to 800 million sperm per dose is the industry standard, but new insemination techniques may allow success with fewer sperm per dose.
  • What is the post-thaw motility of the sperm? 35% is an industry minimum, 65% to 85% or better is expected in a quality product. However, some semen with a low post-thaw percentage gets a very good conception rate, while some semen that looks wonderful fails to achieve conceptions.
  • Has the semen been tested disease-free?
  • What is the stallion’s conception rate with frozen semen? This is important, as there are some stallions who meet the quality semen criteria, but who fail to impregnate mares. With young stallions who haven’t had the opportunity to prove themselves as "frozen sires," you may just have to take a chance with semen that meets the other criteria. If you do, it’s wise to have a backup dose of an "old reliable" frozen sire to use in case the mare doesn‘t settle. It‘s probably best, when using an unproven sire, to use a mare who has settled with frozen semen before, so you‘re not working with two unknown factors. Dealing with reputable producers and brokers of frozen semen is another way of insuring success. They know how to collect, process, handle, transport and store semen to insure quality. They can also provide you with advice and information that will help you achieve a conception. Semen brokers are in a position to hear from many people about their successes and failures with different stallions, and most will pass that information on to their clients.


  1. Purchase enough semen. We recommend buying two or three doses per mare, for two to three heat cycles. Some people prefer to buy one dose of a stallion of their choice, and a backup dose of a stallion that is known to freeze especially well. Your chance of conception with one cycle, and rises significantly with two cycles. Give your mare the same number of cycles to conceive with frozen as you would with another breeding method.
  2. Have a teasing program. This is essential. Do not rely on hormonal manipulation instead of teasing.
  3. Handle and thaw frozen semen properly. Handling and thawing of the semen can have a great influence on semen viability. Any time frozen semen is out of the tank for more than three seconds, cellular damage may occur.
  4. Thaw semen properly. Thawing instructions are included with each shipment.

And that’s all there is to it! Now that you understand the basic requirements for achieving breeding success with frozen semen, here’s hoping you have the final ingredient--good luck!