Mares in Foal

Mares in foal

The ultimate way to pregnancy test the mare is by a rectal ultrasound examination. The mare will be scanned 16 days post cover or 14 days post ovulation. The scan will visualise the pregnancy  and the uterus will have an increased tone and no folds or fluid present. Early scans are very important to try and rule out twins.

•        Mares rarely carry twins to term due to the unique uterine anatomy

•        If twins are undiagnosed, this may lead to dystocia (foaling difficulties)

•        May abort both foetuses (usually around the 8 month mark)

•        It is easier to ‘squeeze’ a twin prior to implantation at day 16

•        Mare is checked 24-48 hours later to ensure one foetus remains and is growing

Positive Pregnancy of one fetus

Positive Pregnancy of one fetus

Positive Pregnancy of two fetus’

Positive Pregnancy of two fetus’

Mares pregnant at 14 days are then scanned at 28 days. At this scan, we should be able to detect a heartbeat. If the mare has reabsorbed her foetus, we should be able to get her to cycle again.

The next scan will be at 35-42 days. Mares that reabsorb after day 32 may not re-cycle again for the season as pregnancy hormones are still having an effect. Pregnancy certificates can be issued at this time.

Other tests are available that detect hormone levels in blood or urine to diagnose pregnancy e.g. Wee-foal-checker test. They can be used by the owner. False positive results may occur if the mare has reabsorbed the foetus prior to collection of the sample, as the hormone levels do not return to non-pregnant levels straight away.

The average gestation length in mares is 340 days, normal can be anywhere between 320 and 362 days.

  • It is safe to continue using "wormers" up until 4-6 weeks before the due date. Most products state if they are safe to use in pregnant mares.

  • Teeth should be done annually either during the early stages of gestation or when she has a foal at foot.

  • Feet can be trimmed throughout pregnancy

  • A vaccination booster against Tetanus and Strangles should be given approximately 6 weeks before the due date. The mare may also be vaccinated against Salmonella, Herpes and/or Rota virus.

  • Mares should have access to shelter

  • Fencing should be such that the foal can’t fall through the wires and into another paddock

  • The mare may require a larger volume of water in late pregnancy, especially if due in the warmer months.

  • Access to good quality pasture is preferable but supplementation with good quality lucerne and/or grass hay can be sufficient. There are many good quality pre-mix concentrate feeds on the market that have been formulated for use in pregnant and lactating mares. Energy requirements will be greatest in the last trimester as that is when the foal grows the most.

Zoe Meyer