The Pros and Cons of Equine Frozen Semen

October 23, 2013

The advantages and disadvantages of utilizing equine frozen semen are debated by stallion and mare owners alike. Will I continue to show my stallion or retire him to the breeding shed? Is there an international market for my stallion? What if my stallion is injured in an accident or suddenly dies? Is my mare a suitable candidate for breeding with frozen semen? Is it true conception rates with frozen semen are lower than those when using cooled semen? These are just a few questions to ask when considering whether to utilize equine frozen semen.

Advantages of Equine Frozen Semen

No Need for On-demand Collections

In previous years it was necessary for a stallion to be either a show stallion or a breeding stallion. If he were to be a show stallion the decision could delay or limit his ability to produce offspring. Many shows take place in the spring and thus interfere with the natural breeding season of the horse. If he were to be a breeding stallion he would be “retired” to the breeding shed and no longer compete. With increased acceptance of frozen semen a stallion owner no longer has to choose…he can do both.

A young stallion builds his reputation based not only on his genetic history but also on his ability to perform in the show ring. To build his reputation he must remain in training, attend shows, and have the opportunity to showcase his talent. The need to retire him to the breeding shed before he has achieved his athletic potential could have a negative effect on the number of breedings he receives. However, if he continues to attend shows mare owners are given the opportunity to witness his ability, view his confirmation and experience his personality, and he also has the chance to win championships. Some choose to offer only frozen semen during the breeding season where others may choose to offer fresh or cooled semen while he is not showing but then offer frozen semen when the stallion is away from home.

When stallions are collected for semen freezing, the collection frequency is typically 3 days per week. This provides the optimum balance of sperm production and semen quality for most stallions. With cooled semen most stallions are collected at least 4 times per week and for some heavily booked stallions they may be collected 6 or 7 times per week and this can last for an entire 5-6 month breeding season. This extensive collection schedule can be very stressful on stallions and may lead to lameness or behavioral problems.

Another added benefit is that when processing frozen semen every bit of the ejaculate is utilized and therefore no semen is wasted. A typical stallion produces enough sperm to make 6 – 8 breeding doses. Most stallions don’t require that many doses be shipped on a particular collection day, so the unrequired semen is often poured down the drain. Alternatively, if sufficient semen remains after cooled semen doses have been prepared, the remaining semen can be frozen and stored for future use.

Access to a Global Market

The proximity of a stallion to a mare used to determine which stallion a mare owner would choose for breeding their mare. With frozen semen and use of the internet the world can be the market for any stallion. Frozen semen can also allow stallion owners to tap into both the Northern and Southern Hemisphere breeding season which can provide year round income.

Though some countries have regulations for the importation of fresh and/or cooled equine semen the logistics make these options nearly impossible. Between the necessary paperwork, flight schedules, distance between countries, and time it takes to clear a shipment through customs the only logical, easy answer is frozen semen.

Frozen semen can be processed to meet published import requirements of any country. The task of deciphering the requirements of some foreign countries can be a daunting and laborious task. It is best to inquire with a facility, like Select Breeders Service, which is well versed in collecting, processing, shipping and clearing equine frozen semen through customs.

Frozen semen can be sent to a foreign country either in small shipments for one or two mare owners or in bulk shipments consisting of hundreds of doses that would constitute multiple breedings. The decision on which to choose is based on what the anticipated market is for a particular stallion’s semen in a certain country. A benefit of sending a bulk shipment to a reputable storage and distribution facility in a foreign country is that the semen is ready and waiting for a mare owner to purchase. It can be shipped immediately and the mare owner need only pay the fees for a domestic shipment, as opposed to the more expensive option of an international shipment. This makes the decision process easier for the mare owner and allows them to have the semen for breeding in a timely manner. The international network of SBS Affiliate Laboratories has enabled many of our clients to distribute their stallion’s frozen semen on the international market, extending his genetic influence well beyond the US breeding base.

Unknown Variables Need Not Dictate the Ability to Breed a Mare When She is Ready

With fresh semen it is necessary for a mare to be in close proximity to a stallion. Cooled semen shipments allow more distance between a mare and stallion as long as she can be bred within 24 to 48 hours after collection. Frozen semen is always available, increasing flexibility for the mare owner.

What if a mare is ready for semen and the stallion isn’t scheduled to be collected for several days? What if the stallion is injured or at a show and cannot be collected? What if weather delays the ability of the semen to be delivered before the mare ovulates? What if a stallion doesn’t produce enough sperm to satisfy the number of doses required on a particular breeding day? What if the stallion dies unexpectedly? If frozen semen is available it can be shipped to the mare owner or vet days, weeks, months or years before it is needed as long as long term storage is available. This is beneficial to mare owners as the semen is at the facility and ready whenever the mare needs to be bred and isn’t dependent on the stallion’s schedule or availability.

The use of frozen semen can also be less costly than cooled semen for a mare owner. When using frozen semen all doses for a breeding season can be sent in one shipment. If using cooled semen only one or two doses can be shipped per cycle requiring multiple shipments per breeding season.

An “Insurance Policy” if a Stallion is Injured, Becomes Ill or Succumbs to Death

The best time to freeze semen from a stallion is when he is young and healthy. All too often the thought of freezing semen does not occur to stallion owners until their stallion is injured, colics, suffers an illness or passes away. If he is unable to be collected for fresh or cooled shipments then frozen semen is an acceptable alternative. Without the availability of frozen semen is the potential loss of current breedings and repeat mare owners, resulting in a substantial financial loss to the stallion owner. If a stallion passes away during the breeding season but has frozen semen in storage the stallion owner can fulfill their breeding contracts for the current year and possibly continue to sell breedings long after the death of their stallion. The length of time to sell breedings after a stallion’s death may be limited by certain breed registries. It is best for stallion and mare owners to inquire with their individual registries for any restrictions.

As well as being an insurance policy for illness or death, frozen semen can be a great back-up to a cooled semen program. For example, if there is insufficient cooled semen available to ship to all the mares required on a particular collection day, some mares can be serviced with frozen semen, or if there is an unexpected semen quality issue after collection for cooled semen shipments, the stallion owner can still service the mares with frozen semen.

Increased Quality Control if Produced by a Reputable Laboratory

Many factors can influence the quality of a dose of cooled semen received by a mare owner or veterinarian. A stallion could have suffered a slight fever or illness, there could have been a problem with the collection, the extender or how the semen was handled and processed. These and many other factors can result in poor quality semen upon arrival, upset mare owners, disgruntled vets and lower pregnancy rates.

With frozen semen a post-thaw analysis is performed by the processing laboratory, so you know in advance the quality of the semen you will be receiving. Also you should be informed about the total sperm numbers in a frozen semen dose and therefore you can be assured you are receiving a full dose of semen. It may sometimes happen that you receive less than the ideal number of sperm in your cooled semen dose, for example if the stallion has many mares to service that day, or has semen quality issues. At Select Breeders Service each dose of frozen semen contains at least 800 million total sperm, and exceeds the industry recommended minimum of 200 million progressively motile sperm/dose.

In addition, the use of frozen semen allows for pre-screening for infectious disease. In the past several years there have been two major disease outbreaks in the USA that have had a major economic impact on the breeding industry. It is SBS policy that all stallions be tested for certain infectious diseases that may be transmittable through semen before entering SBS collection facilities. With follow up testing after the freezing period is finished, stocks of disease-free semen can be produced for distribution.

Timed Insemination Protocols Require Less Palpations

It was previously believed when breeding with frozen semen that a mare must travel to a vet clinic, be palpated every 4-6 hours, and must be bred right at the time of ovulation for a pregnancy to result. With the use of published timed insemination protocols there is a decrease in the number of required palpations, it also allows the mare owner the option of keeping their mare at home and scheduling fixed appointments with their veterinarian. Veterinarians are given the flexibility of monitoring mares one time a day during normal hours without compromising fertility. For more information see our FAQs: My veterinarian says that you must breed mares in the middle of the night with frozen semen because it doesn't live long after thawing, is this true? and Does inseminating with one dose right at ovulation give better fertility than 2 dose timed insemination?

Disadvantages of Equine Frozen Semen

The Initial Costs of Freezing Semen May be More Expensive 

When a stallion is collected for cooled semen doses there is typically no out-of-pocket cost for the stallion owner at the time of collection. The collection, processing and shipping fees are usually covered by the mare owners and paid directly to the collection facility.

When semen is frozen from a stallion the expenses are paid by the stallion owner at the time of collection and processing. Though this does not have to be a negative for the stallion owner. Incurring the cost to freeze semen can allow the stallion owner to keep their stallion in training and in the show ring adding to their earnings during breeding season. For stallions collected offsite it can negate the inconvenience of trailering the stallion to another facility for cooled semen collections. If the stallion is collected on the farm, salaries paid to additional staff to collect semen for cooled shipments during breeding season are unnecessary and can be used towards semen freezing costs instead. Alternatively, fees paid for freezing semen can be figured into the amount of a stallion’s breeding or booking fee allowing the stallion owner to recover their initial investment of collecting and storing frozen semen with each breeding sold.

Are Conception Rates Lower With Frozen Semen?

It was previously believed when using frozen semen one could expect lower conceptions rates than when using cooled semen. It is true one can expect higher conceptions rates when using fresh semen compared to cooled or frozen semen. However, there are few published articles comparing the fertility of fresh, cooled and frozen semen within the same stallion. In one particular study the fertility of cooled semen was less than fresh and the fertility of frozen semen was slightly less than cooled semen. However, in other studies comparing frozen and cooled semen the results have been found to be similar. The overall pregnancy rates after the 2010 breeding season for three farms in Maryland, whose breeding programs are managed by SBS, were 79% for cooled semen and 76% for frozen semen. This study looked at shipping either cooled or frozen semen from 36 stallions to a total of 648 mares.

The fertility of fresh, cooled or frozen semen is highly stallion dependent. However, if a stallion has commercially acceptable frozen semen one can expect 50 – 55% first cycle and 70 – 80% seasonal pregnancy rates. Please visit our Review of Reports for Reproductive Efficiency for more information on expected fertility when breeding with frozen semen.

Not All Stallions Have Semen Which Freezes Well

The standard followed in the industry has been that if a stallion’s semen cools well that it should also freeze well. However, this rule is not always found to be true. If a stallion’s semen does not cool well the process of freezing and storing semen should not be thought of as unattainable. Many factors can affect the quality of cooled semen such as collection technique, collection frequency, processing techniques, etc. If a reputable facility, such as SBS, is used to freeze semen then strict protocols for collection and processing, disease testing, storage, and collection frequency are followed thus increasing the possibility the semen could survive the semen freezing process when it was otherwise believed it could not.

Nonetheless, not all stallions have semen that can be successfully frozen and we don’t fully understand these individual stallion differences Our experience within the SBS Affiliate Network indicates that approximately 75% of all stallions with normal initial semen quality produce sperm that are able to withstand the stresses of freezing and thawing, based on the industry standard for commercial distribution of ≥30% post-thaw progressive motility.

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. Data collected from a large number of mares indicated that pregnancy rates per cycle were reduced in mares aged ≥ 16 years old (<16yr 54% verses ≥16yr 42%). The deposition of semen in the uterus, by natural breeding or artificial insemination, causes a strong inflammatory reaction. This is a natural process designed to remove excess sperm, seminal plasma and contaminants from the uterus. Older mares appear to be less efficient at clearing this natural inflammatory process that follows mating. An inflammatory uterine environment 5 days after fertilization is incompatible with survival of the embryo. Older mares, at risk of developing a persistent inflammatory reaction after semen deposition require additional management at breeding time. Treatment strategies for this population of mares should include prompt correction of anatomical defects of the caudal reproductive tract, limited uterine exposure to semen and bacteria and support of uterine clearance from contaminants and products of inflammation. Ideally, only semen of good fertility should be used in these mares. For more information see our article: Use of Frozen Semen in an A.I. Center: Technical Management and Obtainable Results

When deciding the pros and cons of equine frozen semen there are many factors to consider. Though many myths can be proven false it is best to contact a facility well versed in collecting, processing, storing, distributing and breeding equine frozen semen with any questions.