Body temperature is a valuable parameter in determining the wellbeing of laboratory animals. However, using body temperature to refine humane endpoints during acute illness generally lacks comprehensiveness and exposes to inter-observer bias. Here we compared two methods to assess body temperature in mice, namely implanted radio frequency identification (RFID) temperature transponders (method 1) to non-contact infrared thermometry (method 2) in 435 mice for up to 7 days during normothermia and lipopolysaccharide (LPS) endotoxin-induced hypothermia. There was excellent agreement between core and surface temperature as determined by method 1 and 2, respectively, whereas the intra- and inter-subject variation was higher for method 2. Nevertheless, using machine learning algorithms to determine temperature-based endpoints both methods had excellent accuracy in predicting death as an outcome event. Therefore, less expensive and cumbersome non-contact infrared thermometry can serve as a reliable alternative for implantable transponder-based systems for hypothermic responses, although requiring standardization between experimenters.

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Supplemental material:Figure S1: Slightly increasing body weight during habituation period Body weight [g] at day one and six of habituation period per strain were presented as box plot with median and whiskers [2.5, 97.5 %] (n = 38 C57BL/6J: p-value = 0.0018, n = 15 BALB/cJ: p-value = 0.0004 and n = 15 129S1/SvImJ: p-value < 0.0001, Wilcoxon matchedpairs signed rank test, two-tailed).