Measuring stress: is it all about the hair?

WCVM researchers are investigating the potential relationship between the presence of gastric ulcers and the concentration of hair cortisol in thoroughbred horses. Photo: Myrna MacDonald.

The hair-raising atmosphere of a thoroughbred racing venue is thrilling for spectators and an accepted way of life for people whose livelihoods depend on the racing industry.

But what about stress levels of the highly trained animals at the centre of this multi-million dollar industry?

That’s a key concern for Dr. Fernando Marqués of the Western College of Veterinary Medicine’s Department of Large Animal Clinical Sciences. The clinical researcher recently completed a study confirming the high prevalence of nonglandular gastric ulcers, a potential source of stress, among Saskatchewan thoroughbred racehorses.

In a natural progression from his gastric ulcer study, Marqués teamed up with large animal medicine resident Dr. Alberto Ruiz as well as Drs. David Janz, Bryan Macbeth and Marc Cattet of the WCVM.

Supported by the College’s Equine Health Research Fund, the project was designed to investigate the potential relationship between the presence and severity of gastric ulcers and the concentration of hair cortisol in thoroughbred racehorses.

After talking with Janz about his findings that link high hair cortisol concentrations to long-term stress in polar bears and caribou, Marqués decided to seize the opportunity to investigate cortisol concentrations in the animals he and his team were evaluating for gastric ulcers: “As we were endoscoping the horses, we pulled some hair from them and took serum samples so that we could analyze the cortisol levels afterwards.”

Ruiz, who took on the cortisol study as his Master of Veterinary Science (MVetSc) project, worked on the analysis technique with Janz.

“Since the hair of polar bears and caribou and horses is very different and they come from very different environments, we’re trying to modify the technique to develop one that works for horses,” says Ruiz.

Using this customized cortisol enzyme immunoassay, the researchers plan to compare serum cortisol concentrations, indicators of short-term stress, to hair cortisol concentrations, indicators of long-term stress. Most importantly, they hope to establish a relationship between the cortisol levels and the presence and severity of gastric ulcers.

“If the cortisol increases with stress and if horses with severe gastric ulceration experience pain, then they may have higher cortisol levels than horses with no gastric lesions,” explains Ruiz. “Although we won’t be able to diagnose gastric ulceration just from the results, they may help us to identify horses that are more likely to have gastric ulcers.”

The researchers are hopeful that their study will eventually lead to an inexpensive screening test for cortisol concentrations that will be easily accessible to veterinarians and their clients. Using that information, owners could then make decisions about adjusting management techniques such as feeding frequency and training intensity.

Veterinarians could also greatly benefit from knowing which animals or groups of animals that are most likely affected with gastric lesions. A gastroscopy, the only reliable test for diagnosing gastric ulcers, is expensive and invasive. But cortisol measurements could be used to determine which animals may benefit from direct examination of the stomach. Plus, if a link is established between the cortisol levels and the severity of the lesions, veterinarians could use that information to determine a treatment protocol.

Ruiz points out that a screening device leading to early diagnosis of gastric lesions or ulcers could have a huge economic impact on the entire equine industry.

“Gastric ulceration continues to be of great interest to horse owners and veterinarians. New studies are being published each year that are helping us understand the importance of treatment and prevention of gastric ulcers in horses. If we can discover ways to decrease diagnostic costs and improve on our ability to assess stress in horses, everyone should benefit.”