Stallion Showcase 2025 | Methods for Predicting Foaling 

Foaling season can be a nerve-wracking time for horse breeders, especially when it comes to predicting the exact moment a mare will give birth. Although there are several tools and techniques to monitor and estimate foaling times, the process remains highly variable from mare to mare. With gestation periods that can differ by weeks, breeders need to rely on a combination of science, instinct, and tools to ensure a safe foaling experience. 

Mindy Hubert is a seasoned equine breeder, who specializes in foaling mares at her home in South Dakota. After years of foaling, Hubert notes every mare is different.  

“Some mares go exactly 340 days, others will go closer to 320 or even push past 350. This variability makes it difficult to pin down an exact timeline, even for experienced breeders.” 

Hubert emphasizes while there are a number of indicators breeders can watch for, nothing compares to observing the mare’s physical signs. “I’ve had mares that start bagging up six weeks before foaling, while others wait until the very last second,” she says. For breeders, it’s all about knowing their mares and picking up on the subtle cues that indicate foaling is near. 

Dr. Jenny Sones, an equine reproduction specialist at Colorado State University (CSU), agrees that predicting a mare’s gestation length can be unpredictable.  

“We typically say that mares have an 11-month gestation, or around 340 days,” says Sones. “But this is highly variable between mares. Some may go as short as 325 days, while others could go up to 365.” 

According to Sones, a mare’s previous foaling history can offer clues. “A multiparous mare, one that has had several foals, tends to follow a pattern, so once we know her cycle, it’s easier to predict her foaling date,” she says. But even experienced mares can have surprises. Sometimes, challenges during pregnancy or adverse events can lead to preterm birth or a prolonged gestation, and that can change year to year.” 

With gestation periods varying widely, breeders often rely on various tools to help predict when a mare is close to foaling. One common approach, according to Sones, is assessing a mare’s mammary secretions.  

“We measure the pH and calcium in the mammary secretions,” she explains. “When pH drops below 6.5 and calcium levels rise, we can usually predict foaling within 24 to 48 hours.” 

Sones points out that the pH test is relatively simple and accessible for breeders. “You can use pH strips, or even pool water testing kits. It doesn’t have to be horse-specific, just accurate,” she says. “The strips that measure in increments of 0.2 or 0.5 are really helpful because we’re looking for a drop below 6.5.”  

The calcium test is similarly straightforward, and many farms use titration kits that measure calcium carbonate, commonly known as “hardness,” in the mammary secretions. “When calcium exceeds 300 parts per million, or 10 millimoles per liter, it’s a sign that foaling is imminent,” she says. 

Although these tests are useful, neither Hubert nor Sones believes that technology can completely replace the need for human observation. “One of the gold standards for us is simply watching the mares,” says Sones. “We have cameras set up in each stall, and the staff watches them remotely so they don’t agitate the mares by being too close.” Visual observation allows breeders to pick up on behaviors that might indicate foaling, such as restlessness or lying down frequently. 

Hubert also places a high value on watching the mares closely, adding that experience and intuition play a large role. “When you’ve been doing this for a while, you start to know what looks right and what doesn’t,” she says. “I’ve seen mares act totally fine, then a few hours later, they’re foaling. You have to be ready for anything. “I’ve seen mares show absolutely no signs of stage 1 labor and an hour later, there will be a foal up and ready to nurse. On the other hand, I’ve had mares who show signs of restlessness and being colicky and a few days later, they still have no baby.” 

One technological tool that Sones’ team uses at CSU is a telemetric device called “Foal Alert,” which is inserted into the mare’s vulva. The device consists of two pieces sewn into the vulva that separate when the mare’s lips open during labor. “When the pieces detach, it sends a signal to a call box, which then alerts us by phone that foaling is likely happening,” says Sones. “It’s not perfect—sometimes the mare will rub the device out and give a false positive—but it’s still a useful tool in our toolkit.” 

The “Foal Alert” system isn’t the only option for breeders looking to monitor their mares. There’s also a device that attaches to the base of the mare’s tail to monitor body temperature and activity.  

“There’s some evidence that a mare’s temperature drops before foaling, similar to what we see in other species,” says Sones. However, she notes that the tail sensor is still in early stages of validation and may not be widely adopted by breeders yet. 

Hubert mentions that while devices like these can be helpful, they are no substitute for being present. “At the end of the day, nothing beats physically being there,” Hubert says.  

Despite all the technology available, both Hubert and Sones emphasize the importance of human intervention when things go awry. “Even with the best tools in place, you can’t predict every complication,” says Sones. “There are so many variables. The best safeguard is still having a knowledgeable person on hand to monitor the situation.” 

Foaling attendants are especially crucial in high-risk pregnancies, where things like placentitis or preterm labor can complicate predictions. “In those cases, mammary secretion tests may not work, and devices like ‘Foal Alert’ can’t catch everything,” explains Sones. “That’s when having someone physically present is invaluable.” 

As breeders prepare for the busy foaling season, the combination of technology, physical monitoring, and years of experience will continue to be the most reliable method to ensure a smooth foaling process. As Hubert puts it, “You just have to be ready for anything, and trust your gut when it counts.”