How can I tell if the mare is in foal?

Mares do not usually show much sign of abdominal enlargement until the last three months of the pregnancy. The enlargement is obvious in narrow, light-framed animals, but in larger, broader-framed horses it may be much more difficult to tell. Mammary development is usually obvious in maiden mares during the last month, but in mares that have previously foaled, the mammary enlargement (sometimes referred to as “bagging up”) may not be apparent until shortly before foaling. A normal pregnancy in horses lasts approximately 11 months. Colt foals tend to be carried longer than fillies. Premature foals may be born and survive, with intensive care, after only 10 months of gestation. Foals may be carried three to four weeks over time, on rare occasions.

How can the mare be tested for pregnancy, and what is the best time to do this?

It is important to know whether a mare is in foal. Ideally, she should not be ridden the last five months of pregnancy. Pregnant mares also benefit from extra feeding, particularly in the last three months. There are many different ways of testing for pregnancy, some of which can be done only at certain stages of the pregnancy. Unlike females of other species, a pregnant mare produces a special hormone in the uterus between day 45 and day 120 of pregnancy. Most owners like to have a blood test for the hormone carried out at this stage. Veterinary examination of the genital organs, via the rectum, can be used to check for pregnancy at any stage beyond day 40. More recently, ultra-sound scanners have gained an increased popularity in pregnancy diagnosis. By this means, pregnancy can be detected as early as 12 days after covering, but the scan is more often used from three weeks onward.

What are the signs that indicate the mare is about to foal?

Mammary enlargement is the most reliable sign of imminent foaling. A thick, waxy secretion may be seen dripping from the teats; when this occurs, the mare is said to be “waxed up.” Mares show few other signs that they are about to foal, and seem to be able to exercise some control over the process, often foaling at night when privacy is available. Slackening of the vulva and relaxation of the pelvic muscles and ligaments may be detectable, which also indicate that birth is fast approaching.

Are there any precautions that should be taken on the mare’s behalf during pregnancy?

The largest part of a foal’s development within its dam’s uterus occurs within the last three months of pregnancy. Mares can safely be ridden for the first six months of the gestation period, but after this there may be a risk of causing harm to, and potentially losing, the unborn foal. Extra food, particularly protein, is required during the last three months of pregnancy to support fetal growth. Occasionally, mares may lose a pregnancy very early on, at about 20 to 30 days, if they are starved at this time. Mares that are put in foal very early in the spring may need supplementary feeding. Nursing foals should be weaned from pregnant mares during the seventh or eighth month of the dam’s next pregnancy in order to give the mare a chance to “pick up” in condition. Regular exercise is important for keeping a mare in good condition because pregnancy sometimes interferes with circulation in the hind legs. Extreme cold seems to have no adverse affects on the wellbeing of the unborn foal, and mares should be turned out for daily exercise, blanketed if necessary, rather than being confined to a stable all day.

Owners should also be aware that mares sometimes show signs of being on heat when they are pregnant, usually around 40 to 60 days into the pregnancy. This is not abnormal, and a veterinary examination or blood test can confirm if she is still pregnant. A horse’s placenta differs from that of humans or other farm animals. The actual connection of the supply of blood and nutrients between the fetus and the lining of the uterus is not particularly close. Any reduction of the contact between the fetus and the uterus greatly affects the amount of nourishment that passes between them. This is why twins, which naturally have a separate placenta, are usually weak and poorly developed if born alive, but are more often aborted in late pregnancy. Infection of the placenta produces a similar effect leading to an underdeveloped foal or natural abortion. If vaginal discharge is noted during pregnancy, veterinary attention should be immediate. 

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