How to Predict Foaling

Last Updated on February 25, 2022 by Allison Price

Find out the signs and prognostic instruments that can help you predict your parturition

Your mare was born June 1, last year. Equine gestation takes approximately 340 days (roughly eleven months), so she is due in a few months around May 6. This 340-day average is not a guideline. However, it’s quite normal for mares to foal up to three weeks earlier than anticipated.

Although you would love to be there in case of a problem, that is not possible. There are many things going on this spring. It is impossible to watch the expectant dam from the barn all day. This could cause her anxiety and slow down the process. You’d like to know when she will foal, just as many breeders.

There are tools and signs that can help. Two reproduction-focused vets share their expertise to help you be ready for the big day.

Physical changes

Late gestation, which is Day 250 and beyond, sees mares experiencing several physical changes. Ahmed Tibary DVM, PhD and Dipl. ACT is a professor of theriogenology at Washington State University’s Department of Veterinary Clinical Sciences in Pullman. She advises breeders that they regularly examine their mares to see how she is changing in order to be ready for birth (parturition).

He says that mares can be very variable in how they prepare for foaling. This depends on whether they are older, maiden mares or foals. Premonitory signs that are based on morphological and structural changes in mares can be subtle, making them difficult to spot. They may tell you the mare is getting ready but don’t limit the foaling time to an actual day.

You can monitor certain things to ensure that the mare is moving along normally as she prepares for foaling.

Robyn Ellerbrock DVM, Dipl., says that “the classic physical change” is mammary growth or a significant increase of udder size. ACT is a doctoral candidate at the University of Illinois Urbana-Champaign College of Veterinary Medicine. This can occur up to two weeks before foaling. However, if this happens more frequently than that it can indicate problems such as placentitis (inflammation in the placenta). The mare will begin to accumulate dried secretions at the tips of her teats as she gets closer to parturition, which is usually within the last two to three weeks of pregnancy. This process is known as waxing.

Tibary says, “It’s important to remember that we’re talking about probabilities, not a specific time frame, when a mare waxes.” “About 90% mares will foal within 24 hours to 48 hours. However, some mares may wax longer. A mare may wax for a few days or even for several days. One mare that wailed for more than a week last year was at our hospital. This could be because the mare is in the hospital with a lot of other things going on. If she doesn’t find some quiet time, she might delay foaling.

You may also notice relaxation and an extension of the vulva as well as softening the pelvic ligaments around her tailhead. Ellerbrock explains that you may also notice a change in the shape and size of the foal’s abdomen when the foal is preparing to enter the birth channel.

Tibary says that all of these indicators are positive signs that the mare is progressing normaly in pregnancy as long as she appears fine and stays healthy. “For the purpose of making sure someone is there in case there is trouble, however–particularly for maiden mares or mares that have had problems in the past–we need something more precise. Over the past 40 years, most research has focused on more accurate ways to predict when the mare will foal.

Check on late-gestation mares several times daily (at feeding time, for instance). You can monitor your mares 24/7 with cameras or other devices that we’ll discuss in a moment, as you notice signs of parturition.

Behavioral changes

You can spot subtle changes in the behavior and habits of your mare to help you identify impending labour. Most mares will show signs of early labor (Stage 1) within one to four hours. However, some mares may be in active labor for longer periods of time. These are:

  • Being alert and restless;
  • Lieing down, or getting up and down frequently than usual;
  • Pawing, tail-swishing;
  • To lift the tail, turn around and look at the flanks or bite them;
  • Walking around the pen/stall,
  • Sweating;
  • Curling the upper lip at the flehmen location;
  • Unusual mouth movements and yawning
  • Frequently urinating and defecating in small quantities
  • Eating less than usual or going off-feed;
  • Dripping milk or streaming milk

It can be difficult for some owners to distinguish between signs of early labor or signs of colic. Both cause discomfort. Most mares exhibit subtle signs of colic during the first stage of labor, when they are experiencing uterine contractions and repositioning. Many mares appear to be preparing for bed, or they may circle. Tibary says that as more contractions occur, mares often start to sweat, especially on their necks, shoulders and flanks.

How to Predict Foaling

It is important to keep an eye on the mare’s water intake as well as her manure production. Ellerbrock says that if both are normal, she is probably foaling and not colicking.

Tibary believes that the best person to observe a mare is one who has a good understanding of her behavior and what she does in the pasture or stall. He says that a person who is able to spot subtle behavioral changes in mares can detect them. “Mares follow a predictable routine throughout the day. A mare may begin to behave differently from her usual behavior, which is an indication that something is wrong.

The mare is more concerned with internal changes than her normal routine and feels them.

Tibary states that it all depends on whether you’re watching a mare in a stall, on pasture or out with other horses. Each case is unique. Maybe she is being too quiet or spending more time with her eyes closed. The signs may progress to increased alertness, circling, and other behaviors.

The mare might decide to go on her own or with others horses. She might get frustrated if she is kept in a confined area and begin to pace her stall or pen.

Tibary states that mare owners should be aware of any subtle signs in their mares’ pregnancy, not just before they are supposed to foal.

These behavioral signs can vary from mare to mare. He says, “We have seen mares who just keep doing what they are used to; they eat hay and go about their business as normal until suddenly they go into second stage labor.” Some horses may feel mild discomfort for several days prior to labor.

These signs are more difficult to spot at a veterinary clinic because the observer may not be familiar with the mare. Tibary says, “We don’t know her usual routine.” We changed it and she might be more nervous than usual or not want to show any symptoms. The biochemical tests, particularly the strips for calcium and pH, are very useful in monitoring.

Monitoring Devices

There are many signaling devices, such as Foal-Alerts, Birth Alerts, Foal Alarms, and others. These devices can be used to inform the farm manager, owner, or foaling attendant that a mare could be in or is about to go into labor. Some are attached to the mare’shalter while others are sewn to her vulva. Each device transmits a signal that can sound an alarm or call your phone to a receiver when she is lying down or her vulva lips are spread apart.

Tibary says that while these devices are useful, they cannot replace the visual observation. Most electronic techniques are activated by the second stage labor. In some cases, these alarms may be too late because mares foal quickly. You might be able to reach the barn before the mare has foal.

Ellerbrock also says that in the event of a distocia (difficult to birth), the sensor might not be able to reach the vulva to trigger an alarm.

Ellerbrock says that there are devices for monitoring the mare’s heartbeat and when she’s moving around–looking at the horse’s vital parameters. Ellerbrock also mentions that a company is working on such devices. This would indicate that the mare may be foaling, or colicking.

Closed-circuit TV and webcam are other monitoring options that allow you to monitor the mare from your home or smartphone. You can see signs of labor early before other monitoring methods kick in.

Tibary says that “here at our hospital we continuously watch (on webcam), all the mares being monitored foaling,” and that you can monitor the mare from afar, without disturbing her.

Ellerbrock describes how convenient apps that connect with the webcams are: “You could go out for dinner and pull up the mare on the phone to see what she’s doing,” provided the barn has Wi Fi access.

She says that night-vision cameras are the best choice because they don’t require you to keep a light on at all hours of the night. This could disrupt the mare’s natural circadian rhythms and her decision to foal.

Tests of Mammary Secretion

A variety of biochemical tests can be used by owners and veterinarians to determine when a mare may be near foaling. The classic one relies on electrolyte variations in mammary secretions.

Tibary says, “To do a complete monitoring (which must take place at a laboratory), we can examine calcium, sodium and potassium levels.” The real indicator that a mare will foal is the inversion of the sodium and potassium levels. The sodium level would initially be high but will drop as the mare nears foaling. This point of inversion… indicates that the mare is within 24 hours of foaling.

This is the time to intensify your visual monitoring.

He says that other tests are primarily focused on calcium. This is an indicator of foaling imminent. As the mare nears foaling, the concentration of calcium in her mammary secretions increases. Commercially available test strips include Predict-A Foal and FoalWatch.

These tests reveal that the mare’s calcium secretions are at 200 parts per million. The mare is likely to go into labor if the chances of her going into labor within 24hrs, about 50% within 48 hours, and approximately 85% within 48 hours. There is also a 95% chance that the mare will go into labor within 72 hours.

Tibary says that another method, used in conjunction with the calcium strip test, examines pH levels of secretions. These decrease gradually leading to foaling. Research over the past five years has shown that pH levels in mammary gland secretions are strongly correlated with electrolyte fluctuations. The mare is most likely to foal within 24 hours if the pH is below 6.5. The mare owner and the veterinarian can get a bit more information from these two tests. But not all mares lose their pH the same way.

For example, the pH levels of maiden mares’ milk tends to drop very quickly in the 24 hours prior to foaling. However, those of older mares who have had foals before tend to decline more slowly. Ellerbrock’s research at can help you find these pH ranges.

She says that pH strips should be used in increments of 0.1 or 0.2 units when testing for pH. For detecting subtle changes in pH that could indicate imminent foaling, test strips measuring pH in increments of 0.5 units won’t work.

These tests are not always accurate. Tibary says that there have been mares with very high calcium levels for as long as five days before foaling. He also points out that it could be because their routines have changed. Mares can sometimes delay labor for as much 24 hours. These tests are more predictable in the familiar environment of the mare, Tibary says.

These tests can also be affected by high-risk pregnancies or abnormal mammary gland growth. Test results might be affected by mares and maiden mares who have emitted milk before foaling.

Tibary says that placentitis-treated mares or those who have had surgery to correct colic or other stressors will not be able to pass a reliable test. Then, we can rely on electronic devices and watching them closely.

Although monitoring the milk pH and electrolytes levels of healthy mares is a better predictor than simply evaluating physical changes, it can be costly.

Ellerbrock adds that full panel electrolytes and calcium tests will cost more than the ommercially-available pH strip tests.

Take-Home Message

The length of gestation varies greatly in mares. It is worth keeping an eye on them in late gestation to see if they are showing signs that foaling is imminent. Monitoring devices and milk test kits can all be used to predict the impending birth.

Allison Price
Allison Price

I’m Allison, born and raised in San Diego California, the earliest memory I have with horses was at my grandfather’s farm. I used to sit at the stable as a kid and hang out with my Papa while he was training the horses. When I was invited to watch a horse riding competition, I got so fascinated with riding!