Have you been curious about breeding your mare? Sweet River Equine Clinic, Inc. has an advanced breeding program with both mare and stallion services, in addition to our foaling program. We offer artificial insemination (AI) with fresh, fresh cooled, and frozen semen, as well as embryo transfer and stallion collection.

Every breeding is unique and certain circumstances require special treatments or procedures, but the following will give you an idea of what to expect.

Artificial Insemination (AI) offers an alternative to live cover, which poses increased risk of injury to the mare, stallion, and handlers, as well as increased risk of uterine infection. Fresh, fresh cooled, or frozen semen can be used for AI, allowing clients to breed to stallions virtually anywhere in the world.

The first successful record of AI was in 1780 by an Italian scientist, Lazzaro Spallanzani, who bred a dog with freshly collected semen and later delivered a small litter of puppies. In 1803 Spallanzani continued his studies by placing dog semen in the snow where it became motionless,then warming it and observing that it became mobile once again. The desire to make broader use of better sires led to the widespread use ofAI in many modern breeding programs.. AI can also improve the odds of impregnating a mare with marginal fertility.

It is important to coordinate semen shipments with the mare’s ovulation when using cooled or frozensemen. When the mare is in heat she will need to be checked daily and bred just before ovulation. A mare bred within the 24 hours before ovulation has the highest pregnancy rate. An important aspect to remember when breeding your mare is the quality of the semen. Stallions with low fertility may have much lower conception rates than those with high inherent fertility. If needed, ovulation can be induced using an ovulatory-inducing agent such as Deslorelin or HCG. Ovulation usually occurs approximately 36 hours after Deslorelin administration. After insemination, the mare is checked daily until she ovulates. If she does not ovulate within the 24-hour period from the first insemination she is inseminated a second time.

Cooled Shipped Semen
One advantage of using cooled semen is that the location of the stallion is of little consequence. There is no need to endanger the mare and foal, and owners have a broader spectrum for choosing the ideal stallion based on pedigree or performance traits. Costs associated when using cooled semen can include collection fees, semen extenders, and shipping fees. There may also be costs associated with teasing the mare. Veterinary expenses can include rectal palpations, ultrasound exams, pharmaceuticals, and the actual breeding, as well as board and feed. Please call the clinic for an estimate and any breeding packages that are available. The cost can vary greatly depending on many factors including the fertility and age of the mare and the fertility of the stallion. Also, make sure to check with your breed registry because there may be restrictions when using cooled semen.

Planning and preparation are key to a successful pregnancy with cooled shipped semen. Having a fertile mare is the start of a good pregnancy experience. The mare should be in good health with a regular cycle. She should be bred as close to ovulation as possible. Palpating the mare daily, once in heat, ensures the most accurate timing for insemination. An HCG or Deslorelin injection will be given once the mare develops a mature follicle, and semen will be ordered. The HCG or Deslorelin injection is given to aid the mare in ovulating within 36 to 48 hours. Semen selected to breed the mare is usually ordered when the ovulatory agent is given. The veterinarian will then inseminate the mare once the semen has been received. Depending on how many doses have been sent, and the mare’s ovulation cycle, she can be inseminated again the following day. Our veterinarians will use an ultrasound machine to monitor the mare during her estrus cycle and confirm ovulation. The mare will be checked at 15 to 16 days post-ovulation to see if she is pregnant. The pregnant mare is rechecked at 21 days to confirm a single pregnancy and rule out twins. She is checked again at 30 days and at 45 days for a heartbeat. Some mares are checked again at 60 days gestation. If successful, you should see a foal in approximately 340 days (average gestation length). Feel free to call the office to discuss the routine care of your pregnant mare.

Frozen Semen
Frozen semen is handled differently than fresh chilled, and different techniques are used when inseminating a mare. In some cases the only available semen for a particular stallion is frozen. Frozen semen is also used for stallions that live in other countries. Owners that use frozen semen on mares may need to find out a few things before committing to this breeding method. These include cost, size and number of straws that make up one insemination dose, and the paperwork that will be included for the breed registry. Thawing instructions can also vary and will be determined prior to use. When using frozen semen mares will be examined every 24 hours while in heat until the follicle becomes mature (usually 30 to 35 mm in diameter). Once the mare has a mature follicle, she is given Deslorelin and then ultrasounded frequently to determine ovulation. The mare is inseminated at ovulation, or within 6 hours of ovulation, using a deep uterine horn insemination technique. Some mares can develop an inflammatory reaction to the frozen semen, because there is no seminal plasma present. Mares are checked 12 to 24 hours post insemination and treated accordingly if there is an inflammatory reaction. Most mares are placed on altrenogest 3 days post ovulation. They are checked for pregnancy at 15 days post ovulation and again at 30 days gestation when a blood test is performed to determine her progesterone levels

Routine care for the pregnant mare includes keeping her current on her routine vaccinations and dental care. Pregnant mares should be fed good quality forage and/or green grass and can benefit from being supplemented with Platinum Performance. Pregnant mares can be dewormed with pyrantel or ivermectin during pregnancy. The frequency of deworming and the best product to use are determined by the mare’s environment and fecal exam results. Pregnant mares are given Prodigy (or Pnuemabort K) vaccinations at 5, 7, and 9 months gestation to help prevent abortion from Equine Herpes Virus 1. Pregnant mares are given their pre-foaling vaccinations 4 to 6 weeks before the expected foaling date. These include West Nile Virus, Tetanus, EEE, WEE, Influenza, Rhino and Rabies (if rabies was not given prior to breeding). Pregnant mares are also dewormed with ivermectin at 4 to 6 weeks pre-foaling.

The Stallion. Keep in mind, when choosing your stallion, not every stallion produces the same quality and quantity of semen. When semen is processed there are a variety of extenders that are used to maintain the viability of the sperm. Different extenders are used depending on the stallion’s compatibility and what the semen will be used for. Some stallion’s semen ship better than others. It is important to use the proper extender and the proper amount for each collection. When shipping semen the proper amount of extender is added to achieve a concentration of from 25 to 50 million cells per cc to maintain viability. 500 million cells is considered the minimum number of sperm necessary to accomplish a pregnancy. When shipped, at least 1 billion cells are usually sent in a volume of 20 to 60cc of extended semen. When cooled semen is shipped it is usually used immediately upon arrival. If a second dose is sent it is usually inseminated 24 hours later. Feel free to contact us or the stallion owner if you have questions when choosing a stallion. We can also help with semen collection and semen evaluation

Embryo transfers (ET) can be great for horses that are showing, as they do not need to be removed from their primary use to have a foal. ET is also beneficial for mares that have a hard time carrying a foal to term. Embryo transfers can be pricey though, starting around $7,500, assuming both mare and stallion are fertile.

For embryo transfer the donor mare is bred and her embryo is collected 7 days after she has ovulated. Proper veterinary management is key to having a successful embryo transfer performed. The mare’s exact ovulation time is determined as the donor and recipient mare need to ovulate at the same time. Embryos are collected by uterine lavage with a special flushing media. The fluids are collected using a special tubing that is attached to a filter cup. The contents of this filter cup are then transferred to a search dish and the embryo is searched for using a microscope. Once an embryo is found it is placed in a dish containing a transfer media and washed multiple times. To place the embryo in the recipient mare, the veterinarian will put the embryo in an insemination gun that is inserted through the cervix and discharged into the uterus. In some cases embryos are shipped to a facility that has a herd of recipient mares and then transferred.

​​​​​​​We hope you find this information valuable as you explore the different methods that are available. It is important to do your homework before making a decision on breeding your mare. Feel free to call the clinic to discuss your particular breeding situation.