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Service Information

  • Artificial Insemination


    Towcester Equine Vets is a British Equine Veterinary Association (BEVA) approved centre for artificial insemination (A.I).

    The main advantages of artificial insemination over natural covering are:

    • Improved breeding success
    • Reduced risk of injury to the mare and stallion
    • Wider choice of stallion – semen from overseas and deceased stallions can be used
    • Use of frozen semen throughout the season while the stallion continues to compete


    We recommend all mares have a breeding soundness examination prior to A.I.

    Vulval conformation and cervical quality are assessed, followed by a detailed ultrasound scan of the reproductive tract. This allows identification of many problems that may affect fertility. A uterine swab may be taken as part of this examination which will determine if treatment of the uterus with antibiotics is needed before and/or after insemination.

    A clitoral swab and a blood sample are strongly advised prior to breeding, to screen for Contagious Equine Metritis (C.E.M.). Equine Viral Arteritis (E.V.A.), and Equine Infectious Anaemia (E.I.A.). These diseases are known to reduce fertility and can cause abortion. The samples should be taken after 1st January of the breeding year, and ideally within 28 days of insemination.

    Pre-breeding examination in our stocks at Plum Park Farm

    Frozen A.I. services are offered at Towcester Equine Vets, where group or individual turnout for visiting mares is possible. Stabling and use of a horse walker are also available. Chilled and fresh A.I. services can be performed either at your own yard or at the clinic.


    In these mares we recommend a uterine swab initially, followed by biopsy. This helps to identify endometritis which is the leading cause of poor fertility. Techniques such as low dose and deep uterine insemination are sometimes required. Additional hormone and intra-uterine treatments (flushing antibiotics and anti-inflammatories) may be necessary. Frozen semen is not recommended for these mares. Embryo transfer may be a viable alternative following repeated failure to conceive. Please note, it is not unusual for mares to take up to 3 cycles to conceive.


    Following insemination, the uterus is often flushed with sterile saline, to remove dead sperm and debris. This helps to reduce uterine inflammation. Intra-uterine antibiotic treatments and oxytocin injections may also be given at this time. Ultrasound examination is required 24-48 hours after A.I. to confirm ovulation has occurred at the correct time.


    Ultrasound examinations are performed at 15, 28 and 45 days after ovulation.

    In mares that have ovulated twice, a 14 and 16 day scan is recommended so that a twin pregnancy is not missed. If twins are found, it is very important that one is “pinched” (removed) to prevent abortion of the remaining foetus.

    We recommend pregnant mares receive the following booster vaccinations:

    • Equine Herpes Virus at 5, 7 and 9 months
    • Equine Influenza and Tetanus in the last 6-8 weeks of gestation
    Mare pregnancy


    Semen from your chosen stallion may be available fresh, chilled or frozen. The type of semen chosen will determine how your mare is managed, the frequency of ultrasound examination, and the stage of oestrus cycle at which she will be inseminated. Hormone injections may be used to bring your mare into season, to manipulate her cycle, or to induce ovulation.


    This is suitable when the stallion comes to Towcester Equine Vets for collection, or is situated less than 2 hours drive from the clinic. Following collection, semen will be evaluated, extended if necessary, and then inseminated immediately. An extender will improve sperm longevity and motility. Fresh semen can also be used raw in mares reactive to extenders. This method is the closest to natural cover and can optimise stallion fertility. Once daily ultrasound examinations are required in these mares, to ensure insemination occurs 24 hours before ovulation.


    The semen is collected, processed and the refrigerated. In this state it remains viable for up to 48 hours, allowing the use of semen from stallions located anywhere in this country and Europe. Good communication with the stallion owner is necessary throughout to ensure that the semen will be available at the correct time. This is particularly important for European semen as collections may not be possible every day of the week (usually Friday-Sunday). Please be aware chilled semen may need to be ordered up to 48 hours prior to ovulation. As with fresh semen, daily ultrasound examinations are required in these mares.


    Often, frozen semen is all that is available from competition stallions with a busy schedule. Once thawed, frozen semen has a much shorter lifespan than its chilled or fresh alternatives. In addition, sperm can be damaged during the freeze/thaw process, which may further reduce the percentage of progressively motile, normal sperm. A smaller window for successful fertilisation means insemination must occur as close to ovulation as possible. Therefore, ultrasound examinations are performed intensively; every 4-6 hours. Mares receiving frozen semen must be admitted to Towcester Equine Vets. Frozen semen is most successfully used in young, problem free mares.

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