Non-Invasive Thermal Imaging of Unrestrained Goats in Paddocks: Identifying Optimal Regions for Accurate Body Temperature Measurement

Abstract Infrared thermography technology has many applications in small ruminants, working by detecting infrared radiation emitted from the animal’s body surface to measure temperature variations without direct contact. This non-invasive method enables monitoring of physiological status, identification of heat stress, inflammation, or disease, and assessment of animal welfare. The objective of this study was to evaluate thermal imaging for data collection during hot summers in Mississippi and to assess potential heat stress in goats. Twelve goats, similar in age (5–6 months) and weight (26 kg ± 0.2), were measured weekly (8 measurements total) from June 18th to August 6th, 2025, at the hottest time of day (2:00 pm). The animals were held in a 15 m × 15 m pen inside the grazing paddock, allowing free movement. Thermal images were captured for each animal using a FLIR 75 camera (sensitivity 0.03 °C at 30 °C, field of view 42°, emissivity 95%, distance 3 m). Each image covered the full body and was processed using FLIR Tools software to extract four temperature points: eye (E), ear (Ea), flank (F), and hindquarters (H) (Figure 1). Rectal temperature (RT) was recorded with a digital thermometer to validate the thermal measurements. Data was processed using Excel and SAS 9.4, evaluated for normality with the Shapiro-Wilk test, and analyzed with PROC GLM and correlations. Individual data points showed the following results: E (P 0.001, R² = 0.12), Ea (P 0.001, R² = 0.16), H (P 0.001, R² = 0.15), F (P = 0.0625, R² = 0.01). A combined model including all image data points yielded P 0.001, R² = 0.24. Correlations with RT were E = 0.342, Ea = 0.395, F = 0.191, H = 0.387, indicating the best correlations were for ear, hindquarter, and eye. Further research is necessary to validate this technology for goats in paddocks, including optimal imaging distance and additional temperature points per image. Thermal imaging shows promise as a rapid, accurate, and non-invasive method for monitoring body temperature in unrestrained animals under field conditions.