Estimation of heart rate using Triaxial Acceleration Devices in ruminants

Abstract

Heart rate (HR) in ruminants can be used as a proxy to study energy expenditure, under the assumption that both increase proportionally. In various studies, HR has been estimated using belt-mounted sensors placed around the thorax and synchronized with a watch that records beats every 5 seconds. However, this methodology has limitations, including short battery life, potential discomfort or injury to animals, and the need for frequent checking due to device memory constraints.

In recent years, research has begun to explore the use of triaxial accelerometry devices, as a relationship has been reported between animal body movement and energy expenditure. These devices offer several advantages: they are small, record data at a high frequency (30 data points per second), have long battery life, are easy to attach, and do not bother the animals.

From the data collected with these devices, it is possible to calculate OBDA (Overall Body Dynamic Acceleration), a measure of bodily movement. To obtain a preliminary understanding of whether OBDA correlates with HR and could potentially replace it as a proxy, an experiment was conducted at EEMAC (Faculty of Agronomy), where 10 cows were equipped with both HR belts and accelerometers (placed in a halter on the head).

Initially, a regression model was obtained to estimate HR from OBDA and body weight (BW):
HR = 35.094 + 51.896 * OBDA + 0.047 * BW,
where both parameters were statistically significant predictors of HR.

To evaluate the correlation between estimated and actual HR, a larger dataset will be required, which is expected to be collected in the next stage of the study.