Monitoring cardiovascular and respiratory measurements corresponds to the precision livestock farming (PLF) objective to continuously monitor and assess dairy cows' welfare and health. Changes in heart rate, breathing rate, and oxygen saturation (SpO2) are valuable metrics in human and veterinary medicine to assess stress, pain, illness, and detect critical conditions. The common way to measure heart rate is either manually or with a stethoscope. Under research conditions, heart rate is usually measured with a sports watch chest belt. Breathing rate is obtained by counting the cow's flank movements which is a time-consuming and labor-intensive method that requires training and is prone to human error. No devices are available on the market that enable practical and easy pulse oximetry in farm animals. This study presents a wireless nose ring sensor system (NoRS) composed of thermal and photoplothysmography sensors that attach to the nostrils of four Holstein dairy cows. The NoRS's thermocouple measured the cow's nasal cavity air temperature; an optic sensor measured the IR (660 nm) and RED (660 nm) signals reflected from the cow's nasal septum. Breathing was calculated from the thermocouple signal's center frequency with a fast Fourier transformation or the signal peak count (i.e., oscillations). The breathing rate was compared to breathing observed by concurrently counting the flank movements. Heart rate and SpO2 were measured by integrated pulse oximetry and heart rate monitor module (MAX30101 TinyCircuit) assembled on the NoRS circuit. Heart rate was also measured with FFT and by counting the number of peaks from the optic sensor's raw IR and RED signals. These measures were compared to an off-the-shelf hand-held pulse oximeter's heart rate and SpO2 readings during the same time. The comparisons revealed highly significant correlations for the heart rate readings where the strength of the correlation was sensitive to the method. The correlation between breathing rate and the veterinarian's visual observations was low, albeit significant. Thus, inhale-exhale cycle counting constitutes a more precise approach than flank movement counts. The hand-held device's 96% SpO2 is compatible with near-saturation values expected in healthy cows. The mean NoRS SpO2 reading was 3% less. After further piloting under field conditions, the NoRS will require no animal restraining to automatically and continuously record cows' breathing rate, heart rate, and SpO2.
Keywords: breathing rate; dairy cow; heart rate; oxygen saturation; precision livestock farming; wearable sensor system.
Monitoring cardiovascular and respiratory measurements responds to the precision livestock farming objective to continuously monitor and assess dairy cows’ welfare and health. Changes in heart rate, breathing rate, and oxygen saturation are valuable metrics in human and veterinary medicine that are used to assess stress, pain, illness, and detect critical conditions. This article describes a wireless nose ring sensor system (NoRS) developed to read heart rate, breathing rate, and oxygen saturation from the cow’s nostrils and tested on four Holstein dairy cows. These measures were compared to heart rate and oxygen saturation readings obtained from an off-the-shelf hand-held pulse oximeter and a veterinarian’s concurrent count of flank movements. The comparison revealed highly significant correlations between the heart rate readings and a low, albeit significant correlation for breathing rate. The mean NoRS oxygen saturation reading was 3% less than the hand-held device. Although commonly used techniques for detecting vital parameters such as heart rate, breathing rate, and oxygen saturation only provide information about the time of examination, the NoRS is a wearable device that can monitor cardiovascular and respiratory measurements remotely and over time.
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