Meddleton Equine Hospital

Breeding your Dressage horse can be a complicated matter and one needs be prepared for a considerable investment of time, effort, and money before that perfect foal can be a reality. Horses do not have very high conception rates when compared to other animals. This already low conception rate becomes even lower when we start to factor in common management practices, such as breeding outside the normal season, breeding older mares, and breeding by artificial means.

The highest success rates are obtained with natural cover breeding (80% per season), but access to a desired stallion and the risk of injury to the stallion or the mare are serious considerations. Breeding by artificial insemination with cooled, shipped semen has become commonplace and conception rates average around 70%. When breeding with frozen semen, the conception rates average much lower and the process is much more time intensive and expensive. Breeding by embryo transfer has become more popular in recent years. This method allows the mare to continue in competition by breeding her, then collecting the embryo and transferring it to a recipient mare.

A common scenario is a mare that is retired or given time off from competition to breed. These mares are generally well past the optimal breeding age (3-5years) and are maiden mares (never had a foal before). In fact, older (>8 years) maiden mares have the lowest conception rates. This, combined with the fact that in the majority of cases, these mares are to be bred with shipped (cooled or frozen) semen, reduces the conception rates further. All of these factors make successful breeding a challenge.

So what can be done to help these athletes have foals? The 3 most important factors are timing, uterine health, and sperm quality.

Timing

The majority of mares will be most fertile from May to August. If desired, the use of light therapy and hormones can help mares cycle earlier in the season. Once mares start cycling, they will generally ovulate every 21 days. Ovulation generally occurs while the mares are showing signs of being in heat (interested in the stallion, posturing, frequent low volume urination, clitoral winking).

Insemination or natural cover should ideally be timed so that it happens within 24 hours of ovulation (this is the normal lifespan of the ova). The chances of conception decrease significantly 24 hours after ovulation. This is why timing is so important.

The most accurate way of timing ovulation is through ultrasound examination of the ovaries and uterus. This has become the gold standard in equine reproduction. Your veterinarian will monitor the growth of ovarian follicles and will advise when the time is right to breed based on follicle size, texture, and appearance on the ultrasound. Follow up ultrasound or palpation 24 hours after breeding or insemination can ensure that ovulation has occurred.

It is imperative that the semen is available when the time is right! It is important to know in advance when and how often the stallion owner is willing to collect the stallion, and how much advance notice he needs before collecting. It is important to know when the semen is collected, how long the particular Stallion’s semen lasts in the cooler, how the semen will be shipped (FedEx, Courier, Airlines, etc), and how long it takes for the semen to arrive at your mare’s side after it is shipped. This will require good communication between the mare owner, Veterinarian, and the stallion owner.

Uterine Health

Even if the timing is perfect, pregnancy will not happen unless there is a good environment for the embryo to grow into a fetus and eventually a foal. Your mare should have a uterine culture and ideally cytology performed to rule out a low grade uterine infection that would prevent pregnancy. An ultrasound to evaluate the uterus and ovaries for cysts and other abnormal structures is recommended before trying to breed a mare. A uterine biopsy may also be indicated for mares that have failed to become pregnant in previous years, older mares, or mares that have had many foals.

These procedures are of paramount importance if a mare has had small, weak, or sick foals in the past. Mares that have abnormal estrus behavior, abnormal estrous cycles, or abnormal ovaries on ultrasound may also require blood tests to evaluate their sex hormone levels. Your Veterinarian will be able to advise you what tests are necessary based on your mare’s age, reproductive history, and reproductive examination.

It is important to remember to look at the overall health of the mare; she should be current on vaccines, parasite control, and dental care before she is bred. A breeding soundness exam is a good investment. It will help save time and money by detecting potential problems early on and allowing time to address them before the breeding season is over.

Sperm Quality

Even if timing is perfect and the uterus is healthy, conception will not occur unless the semen is of good quality and has been handled properly. Proven stallions generally have a well established insemination dose and preferred handling protocol. This information should be provided by the stallion owner and should be strictly followed.

However, new stallions should receive a breeding soundness exam to determine the health of their sperm and help determine a successful insemination dose. This usually involves a thorough physical exam, a series of semen collections with cell counts, and microscopic examination of the semen before and after certain manipulations (cooling, extending, storage, etc.).

In most cases the work has already been done, and all that is needed is strong communication between owner, veterinarian, and supplier in order to orchestrate the insemination according to the mare’s ovulation and the sperm’s preferred handling protocol.

Early Pregnancy

Once the mare has been inseminated and ovulation confirmed it is up to Mother Nature. Early pregnancy loss is not uncommon during the first 60 days after conception. For this reason, ultrasonographic monitoring of the pregnancy is essential during this period. The first pregnancy exam should be done at days 15-16. This time period allows for breeding without missing a cycle if the mare failed to conceive.

The next exam should be at 25-30 days. At this time a heartbeat can be seen on ultrasound and your veterinarian can determine if the fetus is still healthy or if there is a twin pregnancy. It is also the latest time at which a pregnancy can be terminated without loosing the rest of the breeding season. Twin pregnancies are generally fatal for the foals and can endanger the mare’s life if allowed to go to term. If a twin pregnancy is terminated after 30-35 days, the mare will not cycle for the rest of the season and another attempt will have to wait until the next year.

The next important check is at or around 60 days. Fetal gender can often be determined at this stage as well. After 60 days, the rate of pregnancy loss decreases significantly and the chances of carrying a foal to term are good. Be aware that trailering a pregnant mare increases the chance of loosing the pregnancy.

Whats Left

All that is left to do is to provide good nutrition, dental care, and routine de-worming and vaccinations for the remainder of the pregnancy. Rhinopneumonitis vaccination is recommended to help prevent abortion. It is given at 5, 7, and 9 months of pregnancy. The routine spring series of vaccinations (Eastern + Western Equine Encephalitis, Influenza, Rhinopneumonitis, Tetanus Toxoid, and Strangles vaccine) and de-worming with Ivermectin should be done approximately 4-6 weeks prior to the expected foaling date. A good quality, broad spectrum vitamin and mineral supplement is advisable.

Getting a mare bred successfully requires advanced preparation and research on the part of the owner. Remember to start early in the season and try to get as much information as possible about the prospective sire. Start monitoring your mare’s cycles and keep track of them on a calendar.

Your veterinarian will be able to help guide you through the process.