Validation of body temperature and heart rate sensors in domestic sheep

Summary

The advantages of low input livestock production on large or unfenced pastures, including high animal welfare, positive impacts on biodiversity and low production costs may be challenged by losses due to undetected disease, accidents and predation. Precision livestock farming (PLF) systems enable remote monitoring on an individual level with the potential for predictive warning. Monitoring body temperature (Tb) and heart rate (HR) could allow for development of early warning systems for not only sickness and behavior, but also oestrus or parturition. In this study, we tested physiological sensors in free grazing Norwegian white sheep in Norway. Forty Tb sensors and thirty HR sensors were surgically implanted in 40 lambs and 10 ewes; 20 lambs in one herd and 20 lambs and their 10 mothers in another herd. Tb sensors were implanted in the abdomen and HR sensors were implanted subcutaneously. Eight (27%) of the subcutaneous HR and eight (20%) of the abdominal Tb sensors were lost during the study period. Two abdominal sensors were found inside the digestive system. ECG based validation of the HR sensors revealed a mean
measurement error of 0.2 bpm (SD 5.2 bpm) and correct measurement quality was assigned in 90% of the
measurements. The maximum HR confirmed by ECG was 197 bpm in a juvenile male and the minimum ECG confirmed HR was 68 bpm in a ewe. Mean active HR was 106 bpm (SD = 17 bpm) for ewes and 128 bpm (SD = 18 bpm) for lambs. Mean passive HR was 90 bpm (SD = 13 bpm) for ewes and 112 bpm (SD = 13 bpm) for lambs. Mean Tb for all animals was 39.6°C (range 36.9 to 41.8°C). We established baseline values and conclude that these sensors deliver an acceptable quality. For a wide agricultural use, the sensor design and implantation method has to be further developed and real-time communication technology added.