At the Veterinary Clinic in Emmeloord veterinarian Ids de Boer conducted a clinical test on a 9-year-old Friesian gelding. When assessing the horse´s movement the horse appeared to make a noticeable extra sound in canter. When the horse breathed in, a soft ´whistling´ sound could be heard. The endoscopy revealed that the horse was affected with a mild form of roaring (laryngeal hemiplegia). De Boer states: ‘This degree of roaring will not hinder the horse´s performances in elementary dressage. However, roaring can be progressive so the degree of roaring can potentially change in the future. Therefore this horse receives the remark ´slightly increased risk´ on the clinical inspection report. It is the buyer´s decision whether or not to purchase the horse with this remark on the report.’
Roaring is a condition defined as a partial or complete paralysis of the muscles surrounding the cartilage and vocal cords in the larynx. This occurs when the nerve (n. laryngeus recurrens) that operates the vocal cord is damaged. Usually the left vocal cord is the one that is affected, but in exceptional cases it can be the right vocal cord or even both.
Floppy vocal cord
The vocal cord is floppy and depending on the degree of roaring this causes a narrowing of the airways. In serious cases this can lead to reduced stamina. Most horses with a mild form of roaring can function normally. Because the vocal cord is less taut, it starts to vibrate when the horse breathes in during exercise, which is what causes the extra sound.
What causes roaring is as yet not quite clear. There seems to be a hereditary factor. Roaring is mostly seen in larger horses, ponies are only very rarely affected. There is also a significantly higher presence of the condition in stallions and geldings than in mares. Other causes for roaring can be when the nerve is damaged due to problems in the air sac, throat (e.g. strangles/glanders) or poll, or as a result of poisoning from heavy metals. Not all horses suffering from roaring need treatment. This is only necessary if the condition poses problems for the horse´s functioning and therefore every individual needs to be personally assessed.