Heart rate sensor validation and seasonal and diurnal variation of body temperature and heart rate in domestic sheep

Summary in the original language of the document

Advantages of low input livestock production on large pastures, including animal welfare, biodiversity and low
production costs are challenged by losses due to undetected disease, accidents and predation. Precision livestock
farming (PLF) enables remote monitoring on individual level with potential for predictive warning. Body temperature
(Tb) and heart rate (HR) could be used for early detection of diseases, stress or death. 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. Eight (27%) of the HR and eight (20%) of the Tb sensors
were lost during the study period. Two Tb sensors migrated from the abdominal cavity in to the digestive system.
ECG based validation of the HR sensors revealed a measurement error of 0.2 bpm (SD 5.2 bpm) and correct
measurement quality was assigned in 90% of the measurements. Maximum and minimum HR confirmed by ECG
was 197 bpm and 68 bpm respectively. 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). Tb displayed 24-hour
circadian rhythms during 80.7 % but HR only during 41.0 % of the studied period. We established baseline
values and conclude that these sensors deliver good quality. For a wide agricultural use, the sensor implantation
method has to be further developed and real-time communication technology added.