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Stud Work 

Breeding mares

Mares can be bred naturally by the stallion (either at pasture or in a controlled environment with the stallion in hand) or by artificial insemination (AI). Artifical insemination is when semen from the stallion is implanted into the uterus of the mare. Timing is everything in this procedure and the sperm must be deposited close to the time of ovulation. Whilst AI is not permitted for breeding Thoroughbreds, it is now a very popular and frequently performed procedure for breeding sports horses.

Mares going away to be bred by natural service are likely to be asked for clitoral swabs for contagious venereal disease and sometimes blood samples for infectious disease. This is now becoming a very routine requirement for stud farms.

What are the advantages of AI?

  1. There is a decreased risk of sexually transmitted diseases and also of other contagious diseases of horses that can be spread when horses are in close proximity.
  2. There is a decreased risk of injury to the mare, stallion and handlers
  3. Semen is evaluated each time it is collected and used meaning that poor stallion fertility can be picked up early.
  4. It prevents stallion overuse: and allows more mares to be bred to a specific stallion. A single ejaculate provides sufficient sperm to be used in several mares.
  5. Access to a wider gene pool. Semen can be imported from abroad and breeders are less limited by geography. Many continental studs will offer a next day courier service.

Prior to breeding

Prior to breeding your mare, a full reproductive examination should be performed using an ultrasound scanner which will allow us to assess her suitability for breeding and highlight any potential reproductive problems. A full reproductive history is very useful, as this will enable prompt initiation of treatment prior to or after insemination if required.

The initial reproductive examination will allow assessment of the stage of your mare's oestrus cycle and will determine timing of repeated examinations prior to insemination. Mares that have had problems breeding in the past may benefit from an endometrial swab or biopsy at this stage which may indicate a requirement for pre or post breeding treatment such as antibiotics. Follicular activity is followed closely alongside other parameters and when the follicle has reached a suitable size for breeding, hormones will be given to induce ovulation

Following insemination, your mare will be checked for ovulation and for post-breeding inflammation. Treatment may be required, especially in older or problematic horses. Provided all is well, we will arrange for your mare to be scanned at 18 days following ovulation. If she is pregnant, we advise that scans be performed at 28 and 45 days to make sure the pregnancy is developing normally.


Mares typically give birth very quickly, often during the night. Signs that birth is impending are udder enlargement, a waxy deposit on the end of the teat and a change in shape of the hindquarters. A mare would normally be expected to pass the foal within 20 minutes of the onset of straining and straining for over 20 minutes without production of a foal should be considered an emergency so please call us straight away. The mare should be up to date with her boosters as she will pass this protection on to her foal through the colostrum and should ideally be wormed within 1 month of foaling.

It is extremely important that a foal is born into a clean environment. Foals have no immunity to disease at birth so remember to clean off the udder, hindlimb and vulval region of the mare when foaling is imminent. It is crucial that a foal suckles colostrum which will give immune protection for around the first 3 months of life. A foal should suckle around 1.5-2L colostrum within the first 8 hours of life and would normally be expected to suckle around half a dozen times every hour. After 12 hours, absorption of immune compounds from the gut is much reduced and after around 24 hours there will be no more absorption by this route. If colostrum from the mare is not available then colostrum from another mare on the same premises is preferred, failing that, a commercial colostrum substitute can be used.

If there is concern as to whether the foal has suckled sufficient colostrum then we can take a blood test to see if this is the case. If a foal has insufficient immune protection he will be very vulnerable to infection and we recommend using commercial immune plasma which can be given intravenously.

We recommend an injection of tetanus anti-toxin soon after birth which will give protection for around 2 months.

Bridgend Branch
Tel: 01656 652751
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Tel: 01443 220580
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Tel: 01446 742800
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Cowbridge Branch
Tel: 01446 502076
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