Noncontact infrared thermometer measurements offer a reasonable alternative to rectal temperature measurement in afebrile horses

OBJECTIVE To assess the repeatability of infrared thermometer temperature readings and evaluate the correlation between digital rectal temperature and infrared thermometer temperatures taken at different locations in healthy afebrile horses. ANIMALS 101 afebrile horses ≥ 1 year old. METHODS Digital rectal temperatures and infrared temperatures from the eye, gingiva, neck, axilla, and perineum were obtained in a climate-controlled environment and at 2 outdoor ambient temperatures (study period, November 1, 2021, to April 30, 2023). RESULTS Infrared temperature measurements were well tolerated by horses, including those resistant to rectal temperature. There was significant correlation between rectal temperature and infrared temperature taken at the perineum (R = 0.57; P < .001) and eye (R = 0.37; P < .001). Infrared temperature measurements were highly repeatable, allowing for calculation of reference ranges for the perineum (36.0 to 37.8°C) and eye (35.7 to 37.1°C) in climate-controlled conditions. There was increased variance in outside temperatures compared to climate-controlled conditions for the eye (P = .002), gingiva (P = .047), and perineum (P = .005). CLINICAL RELEVANCE While infrared thermometer temperatures were not numerically the same as rectal temperature using a digital thermometer, measurements at the perineum and eye were correlated with rectal temperature readings. Further, the repeatability of infrared readings allows for computation of reference ranges that make the infrared thermometer a viable alternative for the practicing veterinarian when obtaining a temperature in uncooperative horses. The infrared thermometer was reliable outdoors for the eye, but not the perineum. Additional validation of infrared temperature reference ranges in febrile horses and warmer ambient temperatures is warranted.