INFRARED THERMOGRAPHY AS A NON-INVASIVE DIAGNOSTIC TOOL OF ASSESSING THE STRESS RESPONSE IN ATHLETIC HORSES DURING ROAD TRANSPORT OVER DIFFERENT DISTANCES.

Horses travel frequently during their life activities, and transport is considered as one of the major stress events [1]. Body temperature monitoring is a valuable resource for assessing welfare, physiological state and stress response in mammals. Eye region offers an ideal location. Previous studies suggest that infrared thermography (IRT) of eye temperature could be useful for measuring stress in domestic animals [2]. Given such considerations, the current study aimed to address whether IRT measurements of eye temperature may reflect cortisol release in show jumping horses subjected to two different transport distances. The study was performed in accordance with good veterinary practices, European (2010/63), and national legislations (DL 2014/26). It compares the effect of two journeys (length: 100 and 300 km; duration: 1:15 and 4 hours, speed: 80 and 75 km/h respectively) on eight adult healthy Italian Saddle horses enrolled after the owner consent (age: 8±12 years old, body mass: 450 ± 50 kg). From each animal, blood sampling, rectal (RT) and eye temperature (ET) assessments were performed before (T1), after (T2) and 60 minutes (T3) from the arrival. Cortisol concentrations were assessed by the obtained serum by species-specific commercial enzyme linked immunoassorbent assay kit (ABNOVA). After blood sampling RT was measured using a digital thermometer. Thermographic acquisitions of ET were performed with a thermal infrared camera (FLIR T440) in left and right eye considering three regions of interest: EL1 (medial canthus), EL2 (central cornea) and EL3 (lateral canthus). For each region Tmax, Tmin and Tavg were automatically obtained. Environmental conditions were recorded inside the truck during both journeys to characterize microclimatic experimental conditions and temperature humidity index (THI) was calculated. Student t-test was applied to verify statistical differences between left and right eye and therefore, mean values of both eyes were used for the analysis. All data were analysed by means of two-way analysis of variance for repeated measures ANOVA (Graph Pad Prism). Statistically significant increase was observed at T2 for EL1max-min-avg (P<0.01), EL2max-min-avg(P<0.01), EL3max-min-avg (P<0.01) and RT (P<0.01) during 100 km and for RT (p<0.01) after 300 km. Cortisol concentration didn’t show significant changes after both journeys. ET values were positively correlated with cortisol and RT at each time points (T1, T2 and T3) during 100 km journey. During 300 km ET positively correlated with cortisol at T2 and T3 and at T2 with RT. It is evident that adult show jumping horses, used to travelling on a monthly basis, are not particularly stressed by journeys. The 100 km journey caused a significant increase in ET and a slight increase in cortisol, although not significant, suggesting that animal doesn’t easily adapt to the new situation in 1 hour. In contrast, maintenance of the studied parameters was observed during the 300 km journey, reflecting the animals' adaptation to transport after 4 hours. This study highlighted the usefulness of IRT as an immediate and non-invasive physiological tool to assess the stress response in athletic horses using an innovative region of interest, allowing practical and fast strategies for monitoring the physiological state of the animal during daily activities.