Establishment of a reference interval and assessment of environmental and biological factors affecting ocular infrared thermography in preweaned dairy calves.

Eye temperature RI in preweaned dairy calves is 37.5–41.3°C; always interpret results considering shade, time of day, and weather.

This study established a reference interval (RI) for ocular infrared thermography (IRT) eye temperature (ET) in preweaned dairy calves and identified key factors influencing ET under commercial farm conditions. Twenty-one calves housed in individual hutches (shaded and unshaded) had ET measured three times per visit during morning and afternoon periods, with rectal temperature (RT) obtained concurrently for comparison. Using a linear mixed-effects model and multiple outputation, the RI for ET was determined to be 37.5°C to 41.3°C. ET was positively correlated with RT (β = 0.5°C per °C increase in RT), and female calves had higher ET than males (β = 0.3°C). Environmental factors significantly influenced ET: calves in unshaded hutches had higher ET (β = 0.8°C), afternoon measurements exceeded morning values (β = 0.2°C), temperature-humidity index was positively associated (β = 0.04), and wind speed was negatively associated (β = -0.1°C). RT was similarly affected by environmental and management factors, with the exception of calf sex. The findings underscore that ET interpretation must account for housing conditions, time of day, ambient temperature-humidity index, and wind speed—analogous to contextualizing RT readings. This study provides a clinically applicable baseline for ET in field settings, enabling veterinarians to distinguish normal physiological variation from potentially pathological deviations when environmental context is appropriately considered.

This summary was distilled by AI and may occasionally misinterpret data. Confirm critical details with the primary literature before clinical application.