Eye Temperature Measured with Infrared Thermography to Assess Stress Responses to Road Transport in Horses

Horses travel frequently during their life activities. Body temperature monitoring is a valuable resource for assessing welfare, physiological state and stress response in mammals, and the eye region offers an ideal location. The current study aimed to address whether infrared measurements of eye temperature may reflect cortisol release in show jumping horses subjected to two different road transport distances. The 100 km journey caused a significant increase in ET, suggesting that the animals did not easily adapt to the new situation in 1 h. The maintenance of the studied parameters was observed during the 300 km journey, reflecting the animals' adaptation to long-distance transport. This study highlighted the usefulness of IRT as an immediate and non-invasive physiological tool to assess the homeostatic adaptation in athletic horses using an innovative area of interest which allows practical and fast strategies for monitoring the physiological state of the animal during daily activities such as road transport. The aim of the present study was to investigate eye temperature modifications after road transport in athletic horses habituated to travel. Eight adult Italian saddle horses traveled 100 km and, two weeks later, 300 km. Eye temperature (ET), rectal temperature (RT) and serum cortisol concentration were assessed before (T1), after (T2) and 60 min (T3) after the road transport. ET was evaluated with infrared thermography (IRT) in three regions of interest: EL1 (medial canthus), EL2 (central cornea) and EL3 (lateral canthus). Two-way analysis of variance (ANOVA) for repeated measures showed statistically higher values at T2 and T3 for EL1 (p < 0.01), EL2 (p < 0.01) and EL3 (p < 0.01) following the 100 km journey. RT (p < 0.01) showed higher values at T2 and T3 after the 100 km journey and higher values at T2 (p < 0.01) following the 300 km journey. ET values were positively correlated with RT at T1, T2 and T3 following the 100 km journey and at T2 following the 300 km journey and positively correlated with serum cortisol concentration at T1, T2 and T3 following the 100 km journey and at T2 and T3 following the 300 km journey. Eye temperature monitoring with IRT allows quick and practical strategies to monitor an animal's physiological state and welfare during daily activities.