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Predicting Foaling: Calving Alert System Might Work for Horses, Too

It’s never easy to know when a mare’s going to foal. Sure, you can detect the approximate month based on a gestational calendar. And you know you’re getting close when you see the udder start to fill. But guessing the precise moment labor will start is nearly impossible—and, unfortunately, most labor detection methods just aren’t very reliable, a research team based in Germany said.

But human presence is critical when a mare foals in case intervention is necessary during a difficult birth, the researchers said. That’s why they recently investigated a new foaling detection system based on an accelerometer. The idea isn’t to check heart rate or up-and-down movements but, rather, “subtle restlessness,” explained Christine Aurich, DVM, PhD, head of the Graf Lehndorff Institute, in Neustadt.

“The restlessness we detected is hardly detectable by the eye of the observer,” Aurich said. “So it is not lying down and standing up. In fact, the mares are often standing quite still, but they show small movements like weight-shifting or minor bobbing of the head. These movements are probably caused by some distress related to stage one of parturition (when the fetus turns).”

Aurich and her fellow researchers followed eight Warmblood, Haflinger, and Shetland mares in late-term gestation. They fitted each mare with a small accelerometer system designed for picking up calving signs in cattle. In cows, the device is attached to an eartag, but Aurich’s team attached the piece to the underside of a halter. With one mare, they used three accelerometers—placed at the underside, along the jawline, and along the side of the face near the eye—to test how their position might affect readings.

All the mares wore the accelerometers in the last few days before foaling. Meanwhile, the researchers monitored the mares’ behavior continuously through on-site inspection and video recordings.

The most marked differences in readings occurred in the last two hours before foaling, with the most notable of those differences occurring in the last 20 to 30 minutes, Aurich said. That means it appears to be picking up the subtle restlessness mares experience shortly before foaling, she said.

They also observed that accelerometer position on the halter did affect the signal detection rate, but that didn’t seem to affect the investigative readings of those signals, Aurich said.

Overall, although it was a small study with only eight horses, they found the accelerometer system to be consistent and reliable, she said.

While the results were promising, they noted areas for improvement in the accelerometer system in horses, Aurich said. For example, the device’s higher position on a cow’s ear gives a better signal detection rate, so the placement might need to be adapted in horses. “A modified neck strap might be a good solution,” she said.

The system could be improved even further if it benefits from a combination of signaling, such as detection of skin temperature changes or lying behaviors, she said. “A combination of independent parameters will almost always improve the reliability of a system,” Aurich said.

Current systems, like those detecting lying behavior alone or heart rate changes, are unreliable because they tend to produce too many false alarms or don’t alarm at all, Aurich said. Unlike other species, mares don’t experience an increase in heart rate at foaling—in fact, they often have a reduced heart rate. And as for lying behavior, it’s extremely variable from one mare to another.

“The lying behavior of mares may be very unpredictable during late pregnancy and foaling,” Aurich said. “There are occasionally mares that do not lie down when foaling, or others that lie down frequently on the side for sleeping during late pregnancy. Both situations are in contradiction to the system’s requirements.”

So far, this accelerometer system appears to be the most promising one for detecting equine labor among the various systems their team has investigated, said Aurich.

“We were quite happy with the results obtained with the accelerometer and suggest that it has a real potential for this purpose,” she said.

The study, “Detection of the time of foaling by accelerometer technique in horses (Equus caballus)—a pilot study,” was published in Reproduction in Domestic Animals.

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