According to a Spanish study, when working horses move to pasture for a lengthy (and well-deserved) break, they’re initially stressed by the change of location. But within a few weeks, their stress levels tend to decrease, allowing them the chance to truly get some “vacation time,” the researchers said.
“It was supposed, from an anthropic (human) point of view, that the relocation was to a better place compared to the working one, with its daily activities, because the new place implied open spaces and no working routines,” said Manel Lopez-Bejar, DVM, PhD, of the Department of Animal Health and Anatomy in the Veterinary Faculty of the Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès).
“But the new space (in our study) also implied changes in daily management and nutrition, less guided activity, and so on,” he said. “Mammals respond to environmental changes with a cortisol (stress hormone) increase. This response is necessary to cope with the new environmental conditions, which may vary as the animals adapts—or not—to these changes.”
Testing Hair for Signs of Long-Term Stress
In their study, Lopez-Bejar and his fellow researchers evaluated cortisol levels in hair samples from eight Pure Spanish stallions of the Municipal Police of Barcelona, Spain, during a three-week off-work period when they were moved to a temporary resting pasture. The team clipped hair from the horses’ abdomens once a month from August to February to analyze it for signs of long-term stress. (Hair samples provide an overview of long-term stressors, while saliva or fecal samples reveal short-term stress, he explained.)
As a control, they ran separate tests on the hair of five police stallions from November to October. This allowed the scientists to study the effect of season alone on cortisol concentrations in hair samples, Lopez-Bejar said. At each sampling, they shaved a section of the abdomen so that only the newly grown hair was collected at the next sampling.
Monitoring Horses’ Adaptation to Changing Environments
The horses’ rest period occurred over the last 22 days of August. After living in individual box stalls during their working season, the horse arrived at their outdoor fields after a 45-minute ride in a horse van, said Lopez-Bejar. At this location, the horses had unlimited forage, no set routines, and no work. They also encountered unknown caregivers and unknown male and female horses.
The researchers noted a significant increase in cortisol, compared to the control horses, related to the change in location for the rest period, said Lopez-Bejar. Despite the welfare advantages of resting, the horses likely experienced stress due to unexpected changes in factors such as “environment condition, housing system, habitual workload, nutrition, changes in staff and support, and social novelty,” he reported.
In other words, the move itself didn’t stress the stallions but, rather, the aspects related to that change of location, Lopez-Bejar explained. “The relocation itself may not be enough to produce an increase of the hair cortisol, but other factors associated with general handling conditions, such as sudden changes in nutrition, housing, exercise, and presence of new horses—to mention just a few examples—could produce an increase in hair cortisol if these new conditions last for a long time,” he said.
Mild Stress—if Short-Lived—Can Be Acceptable
These study results don’t mean “vacation” is bad for horses’ welfare, said Lopez-Bejar. “A cortisol increase does not necessarily mean that the animal welfare is jeopardized, but that the animal is responding physiologically to an environmental change,” he explained.
It has its limits, however: “The cortisol response has to come back to normal when the animal is adapted to the new conditions,” he said. “The issue is when this response is made chronic. It means that the animal is not coping with the stress produced by the change.”
Make Sure Your Horse Has a Good Vacation
To ensure your horse benefits from his time off work, don’t just assume he’s happier in the new place, said Lopez-Bejar. On the contrary, monitor him for signs that he’s adapting over time.
“Owners should consider checking horses’ welfare response when doing any change of management, facilities, etc., and not only before but also during and after the specific change,” he said.
“This would be a preventive action to reduce subsequent problems,” he continued. “Usually, we apply anthropic considerations to horse’s welfare that need to be proved. As it is well-known, the main suggestion is considering a progressive change rather than an abrupt switch in their environment and management conditions.”
While this study focused on Spanish police horse stallions, working horses of different types, breeds, sexes, and situations might have different cortisol responses to environmental change, Lopez-Bejar said.