Infrared thermography (IRT) may be a useful non-invasive tool to assess physiological stress in endurance horses, according to researchers, who suggest it could prove useful in helping vets decide whether horses are fit to continue.
Veronica Redaelli and her colleagues carried out a pilot study in Italy to see whether IRT could be used as a stress indicator in horses trained for the long-distance discipline.
Their findings were encouraging, prompting the study team to suggest that further studies should be conducted at vet checks during endurance competitions to learn whether eye temperature and the temperature at the crown of the head could help vets decide which animals were OK to continue.
Over the last 30 years, IRT has been widely used in veterinary medicine to detect injury, inflammatory responses, and causes of lameness, such as laminitis, in horses.
While its effectiveness as a tool to identify early problems in cases such as laminitis is still a matter of debate, the technique has been used to identify physiological stress in many species, including horses.
In particular, evaluation of eye temperature seems very reliable. It has been successfully used for assessing stress in horses and showed positive correlations with other stress indicators, such as heart rate, heart-rate variability, stress-related behaviors, and levels of the stress hormone cortisol.
Eye temperature has also been successfully used to measure fear-related reactions in horses.
Redaelli and her fellow researchers set up a pilot study to test their hypothesis that the maximum temperature measured with IRT during endurance training varied depending on the intensity. They also examined whether there was any correlation with heart rate and serum cortisol.
The study involved eight Arabian horses, who were tested before and after training at different intensities (low, moderate, and high). All were in work for a 90km international endurance competition for the three months before the study.
The study team documented the effects of the different training intensities on heart rate, blood count, cortisol, and the maximum temperature of different regions – the eyes, crown, pasterns, gluteus, and longissimus dorsi muscles, using IRT.
The results, they said, partially supported their hypothesis.
All the studied parameters increased after training. They found that higher eye temperatures were linked to higher heart rates. Higher temperatures at the crown temperature were linked to higher levels of cortisol.
However, none of the maximal temperatures measured with IRT increased with the intensity of the exercise. Only heart and white blood cells continued to increase as the exercise intensity rose.
The study team said their findings indicated that eye temperature and crown temperature may become a useful non-invasive tool to detect physiological stress during training, and could be used to evaluate how the horses cope with the training.
“Overall, IRT may be used to evaluate the effectiveness of a training regime and to understand how horses are coping with the level of physiological stress induced by the different types of training,” they wrote in the journal Animals.
“IRT would be also useful for identifying overtraining and training-related pathologies and injuries and for preventing prolonged suffering of exhausted horses in competitions.”
The technique, they said, had the potential to enhance endurance horse welfare if used during training and competition seasons.
It may also become a useful tool for the early identification of horses that are not fit to compete or to continue in competitions.
“However, further studies should be conducted on a larger number of horses and during competitions to ascertain our preliminary findings.”
The full study team comprised Veronica Redaelli, Fabio Luzi, Silvia Mazzola and Gaia Dominique Bariffi, from the University of Milan; Martina Zappaterra and Leonardo Nanni Costa, from the University of Bologna; and Barbara Padalino, from the University of Bari.
Redaelli, V.; Luzi, F.; Mazzola, S.; Bariffi, G.D.; Zappaterra, M.; Nanni Costa, L.; Padalino, B. The Use of Infrared Thermography (IRT) as Stress Indicator in Horses Trained for Endurance: A Pilot Study. Animals 2019, 9, 84.