Could Eye Temperature Help Detect Stress in Horses?

Horses’ eye temperatures can accurately reflect their immediate stress levels during show jumping events, said Bartolomé.

Photo: Ester Bartolomé Medina, PhD

If your show jumper is stressed, can you see it in his eyes? Spanish researchers believe you can—if you’re equipped with an infrared thermographic camera, that is.

Horses’ eye temperatures can accurately reflect their immediate stress levels during show jumping events, said Ester Bartolomé Medina, PhD, of the Department of Agro-Forestry Sciences at the University of Seville, in Spain. Such testing could become a very useful tool in the future, she said.

“The main goal of our study was to select those animals that, despite of the environmental conditions they were submitted to during a competition (stress, type of competition, temperature, humidity, etc.), obtained the best sport results and (could) transmit this quality to their offspring,” Bartolomé said. “Stress was only one of the multiple factors that we know can affect sport performance in horses, and we were pleased to find that it could be accurately assessed with this new methodology.”

In her study, Bartolomé and colleagues measured the eye temperature of 173 Spanish Sport Horses at three intervals during two show jumping competitions: three hours before the competition, immediately after leaving the competition arena, and three hours after the competition. They compared these results with those of heart rate monitoring on the same horses at the same intervals.

They found that heart rate increased and decreased in a similar pattern as eye temperature in each individual horse, suggesting that they both result from the same source (stress), Bartolomé said.

Meanwhile, she said, the average heart rate was higher for the 4-year-old horses compared to the other horses. It was also higher in horses that had traveled longer distances (four to six hours) to get to the event and in those that had more hours of daily training (three to six hours per day), she said. By contrast, average eye temperature among horses was not affected by “external” influences such as training programs or travel times, Bartolomé said. But it appeared to be affected by “internal” influences—specifically age and, more importantly, genetic line.

Eye temperature was also associated with performance, Bartolomé said. Horses with higher eye temperatures—suggestive of higher stress levels—averaged poorer performance during the competition than horses with lower eye temperatures. However, the link between eye temperature and performance needs further research to be better understood, she cautioned.

Additionally, the team noted that the Spanish Sport Horse is a relatively new breed made up of a composite of other European sport horse breeds; The researchers examined the differences in results between four main genetic lines: German background, French background, Anglo-Arab (breed arising from a mix of Thoroughbreds and Arabians) background, and a general mixed background from various sources. They found that the highest average eye temperature—reflecting the highest stress levels—came from the Anglo-Arab group.

While Bartolomé does not recommend that owners systematically evaluate their horses’ eye temperatures prior to competitions, she does believe that testing by professionals during competitions could be useful, she said.

Compared to other stress-measurement techniques such as heart rate monitoring and salivary cortisol analysis, eye temperature readings provide a simple, fast, and efficient way to evaluate the horse’s immediate stress level during equestrian competitions.

The study, "Using eye temperature and heart rate for stress assessment in young horses competing in jumping competitions and its possible influence on sport performance," was published in Animal

About the Author

Christa Lesté-Lasserre, MA

Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

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