Breeding your mare - Veterinary Practice
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Breeding your mare

How should veterinary surgeons navigate the myriad of options available to owners looking to breed their mares, and how can they avoid a few pitfalls along the way?

As seasonal breeders, mares are now centre stage following the winter period. Thoroughbreds are mid-season with many mares foaled, covered and safely pregnant, while natives are still heavily pregnant, leaving their owners full of expectation. But pleasure horses are somewhere in the middle given the variety in the owner demographics.

From the outset, a clear discussion of desired outcomes and realistic expectations based on the breeding plan is essential

There are few restrictions to stallion choice and breeding methodologies, resulting in a diverse industry for the attending veterinary surgeon. So, where does the vet begin when they are approached by a client looking to breed their mare? Communication, communication, communication! From the outset, a clear discussion about desired outcomes and realistic expectations based on the breeding plan is essential.

Mediating between desired outcomes and realistic expectations

FIGURE (1) Pinot, Huw’s mare, with one of her foals

Some of the more advanced reproductive technologies have a definite place in our industry and should be embarked on once the client has a thorough understanding of the advantages and disadvantages.

For larger studs, providing a meaningful pregnancy rate is definitely possible: the law of averages means that as a vet, you should be able to achieve close to the expected results. However, for single mare breeders, it is all too easy to be a hero one season and a failure the next. This is especially true when faced with older maiden mares when using advanced procedures such as embryo transfer or ovum pick-up and intracytoplasmic sperm injection.

It is essential to inform the client of the combined likely success rate and not the first step. If we estimate that 60 to 70 percent of mares will be pregnant after first cover with 80 percent of embryos at grade 1 or 2 and that most of these will freeze well, thaw successfully and become healthy pregnancies, when we add up the percentages of the five stages, suddenly it is not unreasonable to suggest to an owner with an aged maiden mare that they may only have a 10 to 20 percent chance of a successful pregnancy from a frozen embryo at each cycle during the season.

Our role is to provide accurate, evidence-based information allowing the client to select the best route for them and their mare

For some owners, this is an acceptable risk as the product is so precious they want to proceed. For others, fully understanding the combined risk may alter their plans and outcomes. Our role is to provide accurate, evidence-based information allowing the client to select the best route for them and their mare.

Pre-breeding checks

All barren and maiden mares should have a vet check prior to breeding. During this examination, the vet can assess every aspect of the mare and undertake the appropriate pre-breeding tests to protect the UK’s high health status.

Specific reproductive diseases such as contagious equine metritis and equine viral arteritis are commonplace in Europe, and it is our responsibility as veterinary professionals to educate our clients and safeguard the UK equine industry. Thoroughbred breeding alone is a hugely valuable industry, and the economic and welfare implications of a poorly identified, reported and managed disease outbreak would be catastrophic.

For current best practice, refer to the 2023 HBLB Codes of Practice or BEVA’s Guide to the Use of Artificial Insemination in Equine Reproduction.

The import and export of horses and germplasm has changed significantly in recent years. Before importing semen or exporting oocytes, it is essential to familiarise yourself with the necessary health testing, documentation and points of entry prior to undertaking mare preparation. (Guidance can be obtained on the BEVA and APHA websites.)

FIGURE (2) One of Pinot’s foals, a little more grown up

Each stud will have a different approach to monitoring mares’ cyclicity and their cover/insemination. In a new situation, the key is to familiarise yourself with their norm and identify the risk areas for errors.

Again, communication and record keeping are essential. For example, finding a follicle is easy, but so is forgetting to document the second follicle and the subsequent second corpus luteum. Being forewarned at the pregnancy scan greatly reduces the chances of missing a twin.


Facilities are also essential, especially as physical (stocks) or chemical restraints are essential for most mares. Mistakes are most frequently made when appropriate facilities are not available, and the vet makes do with what is to hand. Again, this must be documented in the records stall-side to avoid errors at a later date.

Similarly, if someone undertakes a scan on a day different to that suggested by the vet, keep a record. Life is not perfect; it’s healthy to make things work as it keeps us mentally agile; however, taking ownership of these imperfections without documentation or explanation greatly increases stress for the vet.

Pregnancy monitoring

Pregnancy monitoring is a mixed bag! Many mares go from the heartbeat scan to foaling with no checks at all. Others get equine herpesvirus vaccination at five, seven and nine months of pregnancy, while some high-risk mares are monitored throughout with multiple scans and supportive therapy.

Know your mares! Familiarise yourself with the individual and their environment, identify the risk factors and minimise them

So know your mares! Familiarise yourself with the individual and their environment, identify the risk factors and minimise them. Forgetting everything else, small, stable mare groups kept in splendid isolation are surprisingly successful.


Foaling is no different to the above. Every client is an individual, and expectations vary from immediate attendance to nothing more than a tetanus injection. Again, identify the risks. Is the mare high risk? Are the personnel experienced? Does the farm have a history of certain diseases? All the above will build a framework, resulting in an optimal outcome.

Final thoughts

Finally, while horse breeding can divide opinions, personally I can think of nothing better than responsible breeding – supplying our horse-loving owners with their next generation of treasured pets (Figure 1 and 2).

Huw Griffiths

BEVA President, 2021–2022

Huw Griffiths, BSc, BVSc, Cert AVP (Stud Medicine), MRCVS, graduated from the University of Liverpool in 2000 and has a keen interest in equine stud medicine. He is a clinical director and ambulatory vet at Liphook Equine Hospital, and president of the British Equine Veterinary Association (BEVA) for 2021–2022.

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