Comparison of body temperature in dogs and cats using different thermometers

Abstract

Reliable measurement of body temperature is critical in small-animal practice; however, non-contact methods have gained interest for their speed and better tolerance. The aim of this study was to compare, under real clinical conditions, temperatures obtained with a digital thermometer (auricular and rectal) and an infrared thermometer (IR; auricular, rectal, and abdominal) in dogs (N = 35) and cats (N = 15), and to assess the influence of sex, age group, and weight group. Measurements were compiled in a structured database and analysed in SPSS statistical software using descriptive statistics (mean, SD, 95% CI), general linear model for repeated measures with the within-subject factor “site–method” (five levels), and pairwise comparisons with Bonferroni adjustment; as supporting analyses, Pearson correlations were calculated between pairs of methods at the same site. In both species, the main effect of “site–method” was significant (p < 0.001) and showed a consistent thermal gradient with digital rectal as the highest reading, followed by IR rectal, and below these the group of surface measurements (digital auricular, IR auricular, IR abdominal). Post hoc comparisons confirmed that digital rectal was significantly higher than any surface measure and higher than IR rectal; among surface measures, differences were small and not systematic after Bonferroni. In dogs and cats, sex, age group, and weight group did not significantly modify the pattern of differences (no relevant interactions), suggesting that the observed variation depends primarily on measurement site and instrument. Correlations between methods were, as expected, moderate for auricular measurements and low between digital and IR rectal readings and between IR rectal and IR abdominal, supporting that non-contact measures tend to underestimate core temperature. Overall, the results support the use of digital rectal thermometry as the clinical reference, whereas infrared thermometry may be considered a useful complementary tool for screening and monitoring—particularly in less cooperative patients—provided that interpretation accounts for the measurement site and the systematic differences observed relative to the reference method.