A tail-mounted foaling detector used on 17 pregnant mares proved 100 percent successful in detecting upcoming births.
The assessment of the multimodal device was reported in the journal PLOS ONE by researchers in Japan.
It is widely considered desirable to attend to mares at the time of foaling to assist delivery and prevent complications. That being the case, the early detection of the onset of labor is an important issue for the equine industry.
Takahiro Aoki, Makoto Shibata and their fellow researchers said that while a mare’s gestational length is typically 11 months, it can be highly variable between individuals, from 320 to 360 days.
The mare’s second stage of labor, which starts at the rupture of the allantochorion and ends at the complete birth of the newborn, is shorter when compared to other livestock animals, lasting just 15 to 20 minutes on average.
If it exceeds 40 minutes, the percentage of foals born dead rapidly rises.
More than 80% of foalings occur at night. A night watch requires long working hours and is an extra cost to horse breeders.
With the objective of reducing the enormous cost and labor force required by foaling management, many studies have been conducted to predict or detect the time of foaling.
As a result, some physiological and behavioral changes have been described as signs of impending birth. These include a change in body temperature and behavioural changes.
The research team set out to clarify the changes in body temperature and behavior using a multi-modal device equipped with a thermistor (resistance-based thermometer) and a tri-axial accelerometer attached to the tail base. They also examined the ability of the sensor for detecting foaling.
The device monitored surface temperature, roll angle and tail raising, with reference values used to allow the detection of out-of-the-ordinary changes that would indicate an impending birth.
Sensor information was collected wirelessly every three minutes. The unit was able to transmit the data 100 metres without obstacles.
The study team found that the ventral tail base surface temperature decreased before foaling.
A lower surface temperature, a recumbent posture and tail-raising were significantly more common in the last hour before birth than in the preceding 2 to 120 hours.
Precision of 100% was obtained in the study by combining the three data streams – that is, the foaling in all 17 mares was correctly predicted. The same 100 percent precision was obtained by combining just two data streams – the lower surface temperature and lying down.
The study showed that the lying duration and number of lying bouts increased significantly during the last hour before the foal is born.
Tail raising was most common during defecation and urination, they said, followed by foaling-related tail raising.
“Horses defecate 6 to 12 times and urinate 3 to 6 times a day on average. This means the sensor could be useful for detecting health problems such as less frequent defecation or urination.”
The authors said it was not possible to clarify the relationship between the onset of labor and the sensor data.
Because the duration of the second stage of labor is usually short in mares, recognizing the onset of foaling is very important for early detection and appropriate assistance for abnormal births, they said. “It will be necessary to verify how quickly the onset of labor can be detected by the tail sensor before it is deemed appropriate for clinical application.”
No difficult labours were encountered in the study. The usefulness of the tail-attached sensor will have to be reconsidered after further examination of the effects of abnormal foalings on sensor data, they said.
“In the future, by increasing the number of cases, we would like to proceed with a more detailed perinatal behavioral analysis.”
Aoki and Shibata are with the Obihiro University of Agriculture and Veterinary Medicine. They were joined in the study by Guilherme Violin, with the same university; Shogo Higaki, with Japan’s National Agriculture and Food Research Organization; and Koji Yoshioka, with Azabu University.
Aoki T, Shibata M, Violin G, Higaki S, Yoshioka K (2023) Detection of foaling using a tail-attached device with a thermistor and tri-axial accelerometer in pregnant mares. PLoS ONE 18(6): e0286807. https://doi.org/10.1371/journal.pone.0286807
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