Although most mares give birth smoothly, complications such as improper positioning of the foal can quickly become serious. Having assistance readily available during this time can be the determining factor between a successful delivery of a healthy foal and a complete disaster.
Mares typically exhibit few noticeable signs indicating the imminent birth, prompting stud farms to assign someone to monitor expectant mares constantly. On the other hand, individual mare owners may endure numerous sleepless nights while anxiously awaiting the foaling process.
An alarm that reliably indicates the onset of foaling would be extremely valuable.
Researchers in Japan have been assessing the value of a device that detects movement and changes in skin temperature.
Takahiro Aoki and fellow workers used a device consisting of a thermistor and a tri-axial accelerometer, which they attached to the base of the pregnant mares’s tails. A comprehensive report detailing their research has been published in the journal PLoS One.
During the study, seventeen pregnant mares on two private stud farms were closely monitored. The sensors measured and recorded the surface temperature of the ventral tail base, activity intensity, roll angle, and y-axis acceleration every three minutes.
The researchers clarify that the sensors were affixed to the pregnant mares approximately one week before the anticipated foaling date (defined as 335 days from the last mating) and were kept in place until at least one day after the mares gave birth.
The tail sensor collected data on skin temperature (ST) within a range of 20 to 45°C, with a resolution of 0.05°C. It also measured activity intensity within a range of 0 to 102.3, with a resolution of 0.2. Additionally, the device recorded roll angle, which represents the rotation of the x- and z-axes around the y-axis, within a range of -3 to +3 rad, with a resolution of 0.05 rad. Finally, y-axis acceleration was measured within a range of -1000 to +1000 mg, with a resolution of 4 mg.
The researchers discovered that three physiological or behavioural indicators exhibited significant changes shortly before a horse gives birth: (1) a decrease in skin temperature below 35.5°C, (2) lying down (LD), and (3) tail raising (TR).
They investigated the possibility of foaling occurring within one hour after meeting one or a combination of two or three of these criteria.
When considering each criterion individually, they observed a sensitivity of 100% for all three indicators, but the precision was 13.1% for skin temperature drop (LST), 8.1% for lying down (LD), and 2.8% for tail raising (TR).
Combining two indicators resulted in a sensitivity of 100% for all combinations. The accuracies were 100% for the combination of LST and LD, 56.7% for LD and TR, and 32.1% for TR and LST. When all three criteria were combined, both the sensitivity and precision were 100%.
After fulfilling two or more of the indicators, the average to complete labour was found to be between 20 and 30 minutes.
The researchers conclude that the tail-attached multimodal device examined in the study was useful for detecting foaling. “…the time of birth of the foal can be detected with high sensitivity and precision by combining LST, LD, and TR.”
They suggest that the detector may also be useful in detecting when a mare is in season as tail raising is more often seen in mares during the oestrus period.
For more details, see:
Detection of foaling using a tail-attached device with a thermistor and tri-axial accelerometer in pregnant mares
Takahiro Aoki, Makoto Shibata, Guilherme Violin, Shogo Higaki, Koji Yoshioka
PLoS ONE (2023) 18(6): e0286807.
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