If you said “nasal discharge” or “coughing,” you’re on the right track. These are clear, early indicators of potential respiratory disease. But fatigue is the earliest red flag that spurs top sporthorse veterinarian Emmanuelle Van Erck Westergren to think lower airway issues in her patients.
Fatigue takes many forms. In high-performance horses, it could be lagging at the finish line of a race, knocking rails toward the end of a show jump course or a stunted slide into a reining pattern’s finalé.
Whatever form it takes, insufficient oxygen supply is often a cause that takes all but an expert by surprise. The horse may show no other signs of respiratory distress.
“To fuel their physical exertion, horses need oxygen,” explains the founder of Equine Sports Medicine Practice in Waterloo, Belgium. “Appropriate breathing is paramount to deliver oxygen to the muscles and metabolize the energy they require to perform. When they run low in oxygen because of a lower airway condition, their muscles become tired.
“The impact of lower airway diseases like those on the Equine Asthma Spectrum can be significant, especially in high-intensity activities like racing or jumping.
“But in any activity, asthma can lead to premature fatigue and reduced stamina.”
Subtle Symptoms – Prevalent Disease
Don't feel bad if you've missed subtle early symptoms. I happens to the very best equestrians. Equine expert Dr. David Marlin describes several studies in which international-level equine athletes were found to have respiratory disease even though their riders considered them in peak health.
Respiratory issues are surprisingly prevalent.
"We have tracked 400 cases in which horses were referred to our practice for poor performance," says Dr. Van Erck Westergren. "Between 50% and 80% had some degree of respiratory disease. Eventers had 100% and international show jumper shad 85% at the high end, while driving and leisure horses were at the ‘low’ end with 50% affected.
“In a study published in 2019 we found that88% of 731 horses referred for poor performance had Inflammatory Airway Disease, a range of conditions on the milder end of the Equine Asthma Spectrum."
Out of Air Faster
Horses can become oxygen deficient at lower levels of exertion than humans do. Several reasons for this include:
• Horses breathe only through their nose – they are “obligate nasal breathers.” (Try breathing only through your nose the next time you exert yourself for more than a few seconds. It’s hard!)
• Narrow upper airway and the long distance oxygen has to travel from there into the lungs.
• Horses’ bodies are over 60% muscle and muscles are greedy for oxygen. By comparison, muscle mass for a "normal" 18-40-year-old man is 33% to 39%.
• Horses have a higher heart rate and that faster circulating blood means it doesn't stay anywhere long enough to output all the oxygen it carries.
Protecting Fixed Airway Assets
Unlike muscles, respiratory capacity cannot be improved with conditioning, "Respiratory function is a main thing that limits a horse's ability to go to the next level," states Dr. Wren Burnley, a Kentucky veterinarian and active dressage competitor. "You can train, improve or heal just about anything else, but your horse's maximum oxygen output is its maximum oxygen output."
Compromised function at any waypoint in oxygen’s long journey from the nostrils to the lungs limits the full use of whatever capacity our horse has for that oxygen.
"The horse's capacity for acquiring oxygen and using it are not synonymous," explains Dr. Catherine Kohn, VMD Diplomate, ACVIM and many-time United States Equestrian Team and Kentucky Three Day veterinarian. “The bigger the horse, the bigger their lungs, but also the more demand for oxygen. Structural or functional issues and constriction caused by disease and inflammation can make moot any size advantage when it comes to using air supply.”
What You Can Do
Advances in veterinary science form a vast and evolving knowledge base about equine respiratory health. It’s settled science that airborne respirable particles are the biggest cause of non-infectious respiratory problems. It’s also undisputed that the best form of prevention and management is reducing those respirable particles in our horses’ environment.
Haygain’s prominence in the horse health industry has risen on pace with its contributions to the science surrounding respiratory health as critical to all horses’ health, well-being and performance.
Everybody knows that our horses’ most important nutrition source – forage – is dusty. “But the impact of that had not been brought to the fore,” notes Meriel Moore-Colyer, an equine science professor at the United Kingdom’s Royal Agricultural University.
“Together with better diagnostic techniques, like broncho alveolar lavage, we can now see the cellular response to dust in the environment. We can quantify its negative effects on the respiratory system.” That’s why Haygain’s ability to reduce up to99% of the respirable particles in forage make High Temperature Hay Steaming part of the standard of care for horses performing at all levels.
Emmanuelle van Erck Westergren urges owners, riders and trainers to be aware of the signs of asthma in horses and to work closely with their veterinarian to develop an appropriate treatment and prevention plan.
“If left untreated, equine asthma can have serious long-term health consequences,” Van Erck Westergren concludes. “With proper management and treatment, however, horses with asthma can lead healthy, active lives and continue to compete at the highest levels.”