When you think of horses at risk of performance-limiting respiratory disease, which ones top your list? Racehorses? Three-day eventers? While it’s true these equine athletes do require a properly functioning airway to perform at their best, researchers recently identified another group of horses in which upper respiratory tract (URT) disorders appear very common: competition draft horses. What’s more, they tend to develop URT disorders that other breeds typically don’t.
“We chose to study these horses during exercise because previous studies in other breeds have shown us that upper airway problems are more complex than previously thought when based on resting exams,” said researcher Eileen Hackett, DVM, PhD, Dipl. ACVS, ACVECC, of the Colorado State University College of Veterinary Medicine and Biomedical Science, in Fort Collins. “The same is true for draft horses and likely is true for horses of all breeds and uses.”
Hackett and Britta Leise, DVM, MS, PhD, Dipl. ACVS, of Louisiana State University’s School of Veterinary Medicine, in Baton Rouge, reviewed the medical records of 50 draft horses with histories of poor performance and/or respiratory noise during exercise that had undergone both resting and overground endoscopy (putting an endoscope into the airway to observe its function with the horse standing still and exercising normally, respectively).
They identified URT disorders in 46 of the 50 horses (92%) examined. They found complex disorders (two or more URT structures contributing to airway obstruction) in 31 of the 50 horses (62%). Specifically, they found:
- Arytenoid cartilage collapse in 31 horses;
- Vocal fold collapse in 27;
- Aryepiglottic fold deviation in 16;
- Palatal dysfunction in 14;
- Epiglottic disorders in 11;
- Rostral deviation of the palatopharyngeal arch in three;
- Dynamic laryngeal collapse in one; and
- Incidental upper esophageal incompetence in nine.
They also determined that, in most horses (41 of 50), URT disorders, especially pharyngeal and/or laryngeal abnormalities, were only apparent during exercise on overground endoscopy.
The team found the spectrum of conditions affecting competition draft horses to be unique to this discipline, with conditions rarely seen in other breeds or disciplines (including epiglottic deviation). They also concluded that draft horses appear have a higher occurrence of arytenoid collapse than do other breeds.
“Laryngeal neuropathy (dysfunction) is common in draft horses,” said Hackett. “But I think the biggest surprise was that it is an oversimplification to presume laryngeal neuropathy is the only disease of interest in draft horse with upper airway disorders.”
The study, “Exercising upper respiratory videoendoscopic findings of 50 competition draught horses with abnormal respiratory noise and/or poor performance,” was published in the Equine Veterinary Journal.