Use of an Ear Tag-Integrated Temperature Sensor to Depict Temperature Trends in Cows with Normo- and Hyperthermia

Body temperature measurement in cattle is a useful tool for health status assessment and monitoring. To identify sick cows, manual rectal thermometry is still the gold standard. However, this method is labor intense and requires a high amount of time. Continuous and remote measurement of rectal temperature is not possible. The aim of the presents study was to evaluate the use of an ear tag-integrated temperature sensor for detecting dairy cows suffering from fever. First, the reproducibility and accuracy of the ear tag-based thermometers were tested ex vivo utilizing a water bath. Subsequently it was investigated in fresh cows whether the transition from normo- to hyperthermia, determined by thermometry, can be traced via the ear tag-based temperature curves. The measurements from the ear tag-based temperature sensor were very highly correlated with the reference temperature of the water bath (r = 0.99). The coefficient of variation between the ear tag-based temperature sensors was very low (0.82%). It failed to create a general graphical representation of transition from normo- to hyperthermia. The correlation between environmental and ear tag temperature (r = 0.41 - 0.52, P = 0.01) was significantly higher than that between rectal and SB temperature (r = 0.11, P = 0.01). The results of this study indicate that the ear tag-integrated temperature sensors were accurate and repeatable ex vivo. However, the environment seems to have a significantly greater influence, albeit rather low, on the ear tag temperature than the temperature of the animal. While the technology does not serve as an adequate alternative for rectal temperature measurement, it has the potential to passively monitor temperature. Further research is needed to differentiate animal-specific variations associated with disease from other influencing factors.