Horse Breeding made fun with Dr Kirsty Tyler
For those of you that don’t know Australia’s favourite equine Vet Dr Kirsty Tyler from KT equine here is a short intro.
With over twenty years experience in equine practice, Dr Kirsty Tyler grew up in the Bacchus Marsh area before her veterinary career evolved in South Gippsland. After 18 years in Gippsland, where she owned her own practice for 12 years she returned to work for 6 years as an associate at Ballarat Veterinary Practice Equine Clinic. A clinic that excels in equine veterinary care.
Kirsty enters her third decade in the industry with extensive experience in equine reproduction, foal medicine and pregnancy monitoring.
Thankyou Kirsty for teaching us all a little about the basics of horse breeding. For any questions or breeding enquiry’s you can find Kirsty on her Website or Facebook page
Breeding a foal can be an extremely rewarding process. Not only can you continue a genetic line from a mare that you value, it is also possible to access some of the best stallion genetics from Australia and abroad through the use of cool shipped (chilled) and frozen semen. There is also a potential for multiple foals from a mare in a given year with the use of embryo transfer.
Now breeding isn’t for everyone. It is a long-term plan if you are breeding a horse to ride and train yourself. From preparing your mare for stud, getting her in foal, a 340 day gestation followed by another 18 months to 2 years before you can even start your horse.
The Mare
I will preface this section by saying, “Just because you have a good competition mare, it doesn’t necessarily mean she is a good breeding candidate!”
Conformation, age, temperament, genetics, whether she has foaled before and her own ability in your chosen discipline should all be considered prior to going down the path of breeding. Although it is normally very rewarding, it can be expensive, time consuming and on occasion there is heartache involved.
As well as your own thoughts and ideas, I would recommend you seek advice from professionals experienced with breeding. A thorough veterinary examination should be performed by a vet experienced in equine reproduction, before you choose your stallion.
The Stallion
Stallion owners go to a great deal of trouble to have their horses in peak physical condition for breeding season. A stallion that stands at stud has normally reached a high level in his particular discipline or have desirable blood lines to warrant his owners going to the considerable effort and expense of standing him at stud.
Types of Horse Breeding
These days there are three main options to getting your mare bred:
Live Service
The mare is either let run in the paddock with the stallion so that the stallion can serve her when she is in season (oestrus). This requires little to no human intervention and is not overly common these days as the value of horses increases.
Hand service is when the mare is teased to see if she is responsive and ready to cover, and may or may not involve ultrasound examinations of the mare. Experienced breeding personnel will tease the mares every day and keep records of their behaviour towards the stallion or teaser pony, and can reliably predict when a mare is suitable to breed. This in combination with ultrasound examinations can accurately predict the optimal time for breeding. The mare is often mildly restrained with hobbles or a nose twitch and the stallion is led in by the handler to cover the mare. In the thoroughbred industry, live cover is the only way mares can be bred. Insemination with fresh cooled or frozen semen in racing thoroughbreds is not allowed.
Fresh Cooled/Chilled Semen
Semen is transported from the stallion owner or veterinary centre the same day or overnight to be used to inseminate your mare. This has the great advantage that the mare and stallion can be on different sides of the country or even in some cases in a different country (especially in Europe) but we can still achieve high pregnancy rates per cycle.
The mare is monitored via ultrasound examination, and when she has an appropriate size follicle, and showing signs of oestrus behaviour or “being in season” an order for the semen from the stallion owner or collection centre is requested. The stallion is collected and his semen analysed and extended with a combination of antibiotics and proteins to increase its viability. It is then shipped (via a courier) to the veterinarian or artificial insemination centre to inseminate the mare. The mare is often given a drug to induce her to ovulate once her follicle size and behaviour indicate she is getting closer to ovulation so the timing of the insemination can be optimised to be close to her ovulating.
Frozen Semen
This method enables us to utilise overseas genetics or to use stallions that are actively competing and perhaps don’t offer cooled shipped semen.
The great thing about frozen semen is it can be stored at your chosen Artificial Insemination or Veterinary centre indefinitely as long as it is stored correctly in liquid nitrogen at -196 degrees Celsius.
Veterinary examinations take place with the mare to be inseminated for frozen semen often more frequently than for cooled shipped semen, especially around the time of insemination. The frequency of examinations depends on the number of insemination doses available to be used per mare cycle.
Frozen semen can be a little confusing as it is sometimes sold as one or more “insemination doses” depending on the stallion service contract. The number of straws that make up an insemination dose is based on the quality and sperm concentration and will differ between stallions.
The magic number for an insemination dose is 500,000,000 progressively motile sperm. So you need lots of little swimmers to get the job done! Some stallions can achieve this in a four straw dose and some may take eight straws. But the number of straws you need per insemination dose does not necessarily reflect in pregnancy rates, as there are many factors involved in freezing semen. The AI centres that collect stallions to freeze their semen test and measure many different variables (a test freeze) before deciding the most appropriate insemination dose for the particular individual or even if a stallion’s semen is suitable for freezing.
Embryo Transfer
Embryo Transfer (ET) is simply an embryo being removed from one mare’s uterus (the donor mare) and placed into another mare’s uterus (the recipient).
Timing is everything with breeding and with ET this is amplified as the donor mare and the recipient mare need to ovulate at similar times for the best success. If your donor mare’s ovulation is day 0 then the best recipient is a mare that ovulates around a day later (+1) but recipients who ovulate a day before but no more than 3 days after your donor may also be suitable. It is recommended to have up to 3 or 4 recipient mares per donor mare to choose which one is the best candidate.
ET is great for donor mares that are older and considered a high risk (sub fertile) to carry a pregnancy to full term, mares that are currently competing, high value mares that can potentially produce more than one foal a season or younger genetically valuable mares to increase the number of progeny over their lifetime.
The basics are the donor mare is bred using your chosen stallion and at Day 7 post ovulation the mare is flushed using a special catheter and fluid inserted into her uterus and then retrieved through a filter which “catches” the embryo. The filter is carefully washed into a searching dish and this dish is examined with a microscope to find the embryo. It is then washed in a different solution and placed in a holding media.
The most suitable recipient is selected and thoroughly cleaned prior a sterile transfer of the embryo into her uterus. She may receive medication to help her hold the embryo and in another 4-5 days the embryo should hopefully be visible by ultrasound examination.
Horse Breeding Success Rates
Unlike production animal species, the equine industry does not use fertility as a selection criteria. That’s a shame for those of us in the reproduction game!
The pregnancy rates per cycle of all types of breeding depends on many factors. The age of the mare, her reproductive history, stallion fertility, semen handling and timing of insemination all play a part in the success of your breeding program.
For live cover and chilled semen, you can expect anywhere from 50-80% per cycle success rate with good quality semen and timing of insemination.
For frozen semen the internationally accepted per cycle success rate is 30% however a range of 50-70% per cycle is attained with some stallions. You need to expect you will need 2-3 cycles.
Embryo Transfer (ET) has two components to its success rate. The first being embryo recovery (the flush). Success rates depend on the factors mentioned previously and can range from 25-75% per cycle. The second aspect is the transfer of the embryo to the recipient mare. You can expect a 70% per transfer success rate. As such, multiplying the best flush outcome of 75% with a transfer rate of 70% gives an overall ET success rate of 75% x 70% = 52.5% per attempt.
Remember these are guides. Some mares and stallions give greater (and worse) results than these.
How To Optimise your Horse Breeding strike rate
- General health of your mare (teeth, feet, vaccinations, body condition – not too thin or fat and keep stress to a minimum).
- Do your research. Read the contracts for your stallion and your vet clinic and make sure you understand what you are getting for your money. Ask questions if you’re not sure.
- If you’re new to the breeding game, work with people (vets and studs) that you trust or people that are reputable in the industry. These people want a positive result for you and are experienced at what they do.
Happy Breeding Season!
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