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Management of Pregnant Mares

Autumn and winter are generally a quiet time of the year when it comes to horse breeding, so it is easy to forget that broodmares require year-round management to remain healthy, produce a healthy foal, and be in good condition to get back in foal when the time comes. If a mare’s health is neglected over this time it can have a huge flow on effect to the next breeding season.  This artcle covers some important factors to consider with the management of pregnant mares.

Hoof care:

There is a common saying: no foot equals no horse. This especially applies to broodmares, who’s feet are expected to carry the extra weight of the foal during late pregnancy, and are at higher risk of foot conditions such as stress cracks and laminitis. Broodmares should receive regular hoof care throughout pregnancy. Managing body condition in over-weight mares plays a large role in minimising the risk of hoof problems.


Dentistry is a commonly neglected area in broodmares. Regular dentistry is as important, if not more important, in broodmares compared to any other horse since they are expected to grow and produce a healthy foal. Late in pregnancy the developing foal takes up a lot of room in the mare’s abdomen, meaning the mares teeth and digestive system must be as efficient as possible in order to maintain weight and grow a healthy foal. The second trimester is a good time to have a broodmare’s teeth checked. The normal sedatives used for routine dentistry are generally very safe for the mare and developing foal at this stage of pregnancy. The broodmares body condition should be monitored regularly throughout pregnancy.

Herpesvirus vaccination:

Herpesvirus is a contagious disease of horses, which can cause respiratory symptoms and abortion. This virus has the ability to cause latent (hidden or dormant) infections in apparently healthy horses. These carrier horses harbor the infection which can be reactivated if the horse is stressed, for example by transporting to a new environment or to a sale, or by some other illness. There is currently no way of identifying such carrier horses which have the ability to infect susceptible horses.

Aborting mares show no signs of illness but suddenly abort or give birth to a sickly or stillborn foal. Abortions due to Herpes are usually occur after the fifth month of pregnancy. The abortions can occur sporadically but in some outbreaks as many as 75% of in-contact mares may abort. This can obviously be a devastating event when it occurs.

Vaccination plays a major part in the control of this disease, and offers the best insurance against the risk of an abortion storm causing major financial losses. Vaccination should be thought of as good insurance as although there is a cost involved this is little compared to the abortion of a foal due to an infection that was preventable. Pregnant mares should be vaccinated against Herpesvirus at 5, 7 and 9 months of pregnancy. The vaccine is extremely safe and is routinely used to vaccinate pregnant mares to protect the foal they are carrying. There is no risk to the foal from vaccination. A service contract may also require herpes vaccination of the mare in case of a free return of service when the mare loses her foal due to abortion.

Other management procedures that help to prevent spread of the virus include; careful hygiene, avoidance of stress at critical times, and isolation of new arrivals and pregnant mares.

Tetanus and strangles vaccines:

Broodmares should be up to date with tetanus and strangles vaccines, and should receive a booster vaccine 4-6 weeks before foaling. As well as protecting the mare at this time of high risk, the booster vaccine encourages antibody production which passes on to the newborn foal, providing them with some protection against these diseases in the first few weeks of life.

Scanning ‘at risk’ mares:

Mares with a history of abortion, or those that are at higher risk of abortion (e.g. older mares, previous damage to the reproductive tract) are sometimes scanned monthly during late pregnancy to monitor the health of the pregnancy. During these scans the thickness of the placenta is measured. A thickened placenta is an indication of infection or placentitis. Mares found to have an abnormal scan may then be put on medication to protect the pregnancy, and reduce the risk of abortion.

Regular checking:

Throughout pregnancy broodmares should be checked daily for any sign of lethargy, reduced appetite, vaginal discharge, and/or early udder development, as these may be a sign of infection and/or abortion. If any of these symptoms are seen your Veterinarian should be contacted as soon as possible.