The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.
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YOUR GUIDE TO THE 2017 AAEP CONVENTION A50 TheHorse.com/AAEP2017 AAEP Wrap-Up THE HORSE March 2018 ERICA LARSON; CLAIR THUNES, PHD How Pulmonary Disease Impacts Equine Performance P inch or put a kink in a hose, and wa- ter doesn't flow freely. The same can be said for a horse's airways, which supply his body with the oxygen it needs for energy production. And while other body systems generally adapt well to exer- cise, the respiratory system is less capable of doing so, making it an important one for veterinarians to understand. "Horses need 100% respiratory capac- ity to perform at their best," said Laurent Couëtil, DVM, PhD, Dipl. ACVIM, profes- sor and section head of large animal internal medicine at Purdue University's College of Veterinary Medicine, in West Lafayette, Indiana. He reviewed how pul- monary disease can impact performance. Energy required for muscle contraction is produced via anaerobic or aerobic me- tabolism. Anaerobic metabolism requires stored substances such as glycogen and, while it produces bursts of energy, it's not sustainable. It also produces lactic acid, which leads to muscle fatigue and sore- ness. Aerobic metabolism requires oxy- gen; while it's produced at a slower pace, it lasts longer. In most cases, said Couëtil, horses use aerobic energy and, so, must be able to consume oxygen optimally. Fortunately, he said, horses' large hearts and lungs are geared toward taking in and using oxygen for energy production. Yet, the respiratory system is "the limiting fac- tor for performance," Couëtil said. "Even a mild degree of airway obstruc- tion or pulmonary disease may further compromise oxygen delivery to tissues and potentially lead to decreased perfor- mance in horses exercising at or above VO 2 max (maximum oxygen consumption rate), such as racehorses," he added. Pulmonary diseases that can reduce performance include: ■ Mild equine asthma (inflammatory airway disease, IAD) One effect of mild asthma is increased mucous accumula- tion in the airways. Researchers have found that mucous scores of 2 and higher and 3 and higher are associated with decreased performance in race- horses and sport horses, respectively. ■ Severe equine asthma (recurrent airway obstruction, RAO or heaves) Studies have shown that horses with severe asthma fatigued sooner than unaffected horses and exhibited signs of decreased respiratory capacity. Researchers learned that feeding affected horses a low-dust diet and omega-3 polyun- saturated fatty acids can help improve respiratory function. ■ Exercise-induced pulmonary hemor- rhage (EIPH) Scientists have long studied EIPH's impact on racehorses. Findings include: As EIPH score increases, so does the affected horse's distance behind the winner; horses are less likely to win races as their EIPH scores increase; and Grade 4 EIPH is most likely to impact finishing position. Understanding how pulmonary disease impacts performance can help veterinar- ians diagnose and treat issues that could be impairing horses' athleticism. Airway Disease in Sport Horses: Listen, Look, Sample Frequent coughing, increased respi- ratory effort, and nasal discharge are obvious signs of pulmonary disease in horses. But not all signs are so apparent. In fact, said Renaud Léguillette, DVM, MSc, PhD, Dipl. ACVIM, ACVSMR, the less discernable clinical signs are what most frequently accompany equine lower airway disease, making it challenging for veterinarians to diagnose. Léguillette, an associate professor of equine internal medicine and Calgary Chair in Equine Sports Medicine at the University of Calgary Faculty of Vet- erinary Medicine, in Alberta, Canada, reviewed tools veterinarians can use to diagnose pulmonary disease, focusing on noninfectious inflammatory conditions. Respiratory issues are some of the most frequently diagnosed conditions in sport horses evaluated for poor perfor- mance, he said, and one of the leading causes of training disruptions. Knowing the clinical signs of lung pathologies allows veterinarians to col- lect the most relevant information from owners to increase diagnostic accuracy, ARND BRONKHORST Helping Horses Breathe Better AAEP @AAEPHorseDocs Dr. Toll: The leading cause of poor performance in a horse is overexpectation by its owner. #AAEP17