What affects heart health in event horses; therapeutic riding and equine welfare
In both horses and humans, the autonomic nervous system is largely responsible for things we take for granted—regulating our cardiovascular, gastrointestinal and other systems without our conscious involvement. There are sympathetic and parasympathetic aspects of the autonomic system. The former is connected with a fight-or-flight response, while the latter is related to a “rest-and-digest” mode, explains Olivia Lorello, VMD, CVA, from the Swiss Institute of Equine Medicine at the University of Bern.
The two sides are meant to balance out. “When one is high, the other is low,” says Dr. Lorello. A chronic imbalance is a strong indicator of potential heart trouble. And that makes it an interesting area of study for the eventing world, which has been haunted in recent years by a number of heart-related equine fatalities.
Dr. Lorello and her colleagues wanted to begin defining normal values of autonomic tone markers and how they change over a competition season—something that to date has been incompletely described in event horses.
The team gathered two groups of warmbloods, all approximately the same age. The control group consisted of eight noncompeting horses and the test group consisted of 17 eventers competing at Preliminary through CCI*** levels. Not all horses completed the study for either rider-related or horse health-related reasons.
The researchers defined three stages of the competition year: preseason, midseason and peak or end of season. At each of these stages, they measured common markers of autonomic tone, including heart-rate variability, blood pressure, pre- and post-exercise cortisol and muscle-enzyme activities. They also incorporated standardized exercise tests (SETs), where the horses were galloped in three sets for 1,490 meters at increasing speeds with five-minute trot breaks between sets.
“Blood samples were drawn after each gallop,” says Dr. Lorello. “The horses had continuous electrocardiogram monitoring throughout the riding test to measure heart rate and rhythm. This device also had a GPS tracker to monitor speed.”
Researchers found that the eventers in the test group had lower heart-rate variability than the controls, suggesting that the event horses were maintaining autonomic tone balance. Similarly, post-exercise cortisol was lower in the test group than the control group at mid-season and peak season. This indicates that the eventers had a lower stress response to the SETs than the control horses. Not surprisingly, eventers also demonstrated higher fitness levels during the SETs.
Dr. Lorello states that these results don’t yet lead to a specific conclusion regarding event horse heart health. But, she notes, “This study serves to bring us one step closer to understanding the potential effects of training [and] exercise on equine athletes.” And the more we know, the more we can work toward creating an environment of optimal well-being for our horses.
Therapeutic Riding and Equine Welfare
We know that horses can have therapeutic effects on humans in numerous ways. But how does therapeutic riding affect the horse’s welfare? Is it a healthy occupation for our equine friends? A group with the University of Missouri-Columbia College of Veterinary Medicine Research Center for Human-Animal Interaction wanted to find out.
The team, led by the center’s director, Rebecca A. Johnson, PhD, RN, FAAN, FNAP, piggybacked this study onto work it was already doing with military veterans. The veterans suffer from post-traumatic stress disorder (PTSD) and were participating in a therapeutic riding program at the Clear Creek Therapeutic Riding Center. (See the August 2016 “Health Update” or go to www.PracticalHorsemanMag.com).
Five horses were included in the study, which was broken into two six-week sessions. In Session 1, the horses were ridden by the veterans. In Session 2, they were ridden by experienced equestrians. Dr. Johnson and her colleagues measured the horses’ physiological stress indicators, including plasma adrenocorticotropic
hormone, glucose, cortisol levels and behavioral biomarkers. In each session, blood was drawn at multiple intervals: on a resting day; before riding on Weeks 1, 3 and 6; after tacking up; and after each riding class. Behavioral biomarkers were evaluated before each blood draw.
The researchers found that when the veterans were in the saddle, the therapy horses’ cortisol levels were higher before and after riding than on the resting day, while it was just the opposite with the experienced equestrians. Glucose levels, on the other hand, actually dropped after the veterans rode, compared to the resting day.
Overall, both cortisol and glucose levels tended to be higher with the veterans than with the experienced riders. However, the horses’ stress behavior scores were significantly lower with veterans versus experience riders.
Although the results were mixed, the researchers noted that all stress indicators remained within normal ranges for both groups. They concluded that carrying riders with a disability does not stress the horses or negatively impact their welfare—which sets up a win–win–win situation for the riders, the horses and the therapy programs.– Sushil Dulai Wenholz
Researchers are taking a deeper look into the autonomic nervous system in event horses.
Studies have shown that therapy horses do not seem to have elevated stress levels during sessions with disabled riders or military veterans with PTSD.