Young, athletic horses, such as Thoroughbred yearlings and racehorses, frequently suffer a disorder of the larynx called arytenoid chondritis or inflammation of the arytenoid cartilages. Veterinarians once thought that bacterial infection due to inhaled particles was the cause of the inflammation, but a new study* suggests otherwise.
The arytenoid cartilages make up an important part of the larynx, which is located at the end of the nasal passages near the trachea. Most horsemen recognize that dysfunction of the left arytenoid cartilage is the culprit in roaring. Any condition that affects the horse’s respiratory tract negatively impacts performance, including arytenoid chondritis. Rather than focusing on an external cause of arytenoid chondritis, such as bacterial infiltration, an Australian research team put forward an alternate explanation: gastroesophageal reflux, known commonly as heartburn.
If horses can’t vomit due to their super-tight muscular sphincter located at the junction of the esophagus and stomach, is it reasonable to propose that gastroesophageal reflux contributes to arytenoid chondritis and poor performance? Based on new information, the answer may be yes.
In humans, arytenoid chondritis commonly occurs in those with gastroesophageal reflux. Because there is no data on gastroesophageal reflux in horses, and it is currently unknown whether horses are even capable of reflux, researchers placed pH recorders in the esophagus of Thoroughbred yearlings for four 24-hour periods. Key findings were:
- Horses experience gastroesophageal reflux despite the tight sphincter that separates the esophagus and stomach;
- Esophageal pH fluctuated frequently and varied between 4.9 and 9.7; and
- Time after concentrate feeding and time of day impacted esophageal pH.
In light of these data, the researchers wrote, “The findings of this study challenge current belief that the cardiac sphincter prevents gastroesophageal reflux in normal horses, and further build the hypothesis that arytenoid chondritis might be caused by acid trauma of gastroesophageal reflux to the laryngeal mucosa.”
“This is the only published study to examine the relationship between esophageal pH, arytenoid chondritis, management practices, and environmental variables in horses. Additional research is welcome in this field,” added Kathleen Crandell, Ph.D., a Kentucky Equine Research (KER) nutritionist.