A horse that is recognised to be a roarer typically produces a whistling or roaring sound whilst carrying out fast work. This is due to degeneration of the nerve that causes muscles to open and close the larynx. This damage to the nerve can occur in horses that are known to graze on pastures containing Flatweed or Catsear.
It is recognised that in 90 per cent of cases, the left hand side of the larynx is paralysed. Consequently, the vocal cords and arytenoid cartilage are left hanging and when the horse breathes in, the result is this unusual sound.
Diagnosing a Horse with Laryngeal Hemiplegia
Horses can often be recognised with having this problem due to the noise that they exhibit at the gallop. It is then possible to confirm the suspected problem endoscopically. This involves placing an endoscope down the horse’s windpipe to observe the larynx.
Horses that have been diagnosed as roarers can be treated surgically for the problem. If the horse is performing satisfactorily the idea of surgery may be overlooked despite audible sounds when the horse is in work.
Issues with a Horse that is a Roarer
Horses that are known to make a roaring sound whilst being worked may also show signs of not handling heavy exercise loads. This is due to the fact that the job of the larynx is to permit adequate airflow to the lower respiratory tract whilst the horse is galloping. It also works to prevent aspiration of food material when the horse swallows.
Consequently, a larynx that isn’t performing its function correctly can affect the amount of oxygen the horse has access to when carrying out strenuous exercise. The result can be a horse that is easily tired and not performing to its best ability.
Yearlings that are prepared for sale and a future of racing are scoped upon sale at an auction. If they do not pass the scope due to paralysis of either side of the larynx appearing to not function properly, the highest bidder is not obliged to purchase the horse. This is due to recognition of how this problem can affect a horse’s capabilities to gallop.
Managing the Horse that Roars
It is possible to have surgery carried out on the horse that roars. Treatment may involve the tying back of the side of the larynx that is paralysed or there is the option of having a tube inserted into the trachea. This allows the horse to breathe more easily due to bypassing the obstruction in the larynx.
The issue with this form of management is that daily removal and cleaning of the tube is required, turning this management method into a time consuming and ongoing form of treatment. Having a hole into the trachea puts the horse at risk of inhaling debris or water if it has access to large water areas such as rivers or a dam.
The horse that is recognised as a roarer or whistler can be managed effectively. However, for the horse owner that doesn't require their equine to do fast and strenuous work, it may be possible to continue on as normal without having to carry out any operations or other management procedures.
Source
- Veterinary Notes for Horse Owners, Captain M. Horace Hayes FRCVS. Edited by Peter D. Rossdale PhD, FRCVS, Ebury Press, London. ISBN 0 09 171511 3
Chris Thomas - C. Thomas has studied and worked with horses since 2001. She teaches horse studies part time and is undertaking an Equine Science ...
