Thermographic analysis of physiological conditions and after exercise in classic equestrian horses

Few studies have associated horse skin temperature with the thermal environment, physiology and exercise. This study aimed to use infrared thermography to analyze thermoregulation in horses during training and the efficiency of bathing time in restoring normal physiological conditions. A completely randomized design was used, with 2 treatments and 6 replications. The treatments were different bathing times, after exercise: BE – Before exercise (Control – resting animal); T2 – 2-minute shower, after exercise; T5 – 5-minute shower, after exercise. Six Brazilian Sport (BH) and six Thoroughbred (TB) horses were studied, with average age and weight of 8.5 years and 415 kg respectively, ridden over a classic showjumping course for 50 minutes. The variables were collected from 13h00 to 15h00 over 3 nonconsecutive days, before jump training, prior to bathing (post-training) and after bathing. The environmental variables (wet bulb temperature, black globe temperature, relative air humidity and dry bulb temperature) were determined in the external (track) and internal (bathroom) environments. Thermal comfort indexes were calculated: Temperature and Humidity Index (THI), Black Globe Temperature and Humidity Index (BGHI). Were collected the rectal temperature, respiratory rate and body surface temperature. A significant effect was observed for the rectal temperature, respiratory rate and surface temperature (P<0.05) between the pre- and post-training and before and after bathing. Training for around 50 minutes increased respiratory rate as well as rectal and skin temperatures. Bathing times of 2 or 5 minutes promote equivalent reductions in the animals' respiratory rate and skin temperatures, reaching values below those observed before training. The rectal temperature of the animals remained high even after bathing, indicating delayed recovery in relation to the other variables.