Page 706 - The Veterinary Care of the Horse

• The nose should never be packed as horses breathe through their noses so this would

prevent them breathing properly and cause distress.
VetBooks.ir • If the bleeding is profuse or continues for more than 15 minutes, request urgent

veterinary help.

Remember that the average Thoroughbred horse has approximately 50 litres of blood, so
although the horse appears to be losing a lot of blood, it may not be critical.

RECURRENT LARYNGEAL NEUROPATHY (RLN)

This condition is also known as laryngeal paralysis, idiopathic laryngeal hemiplegia and
idiopathic laryngeal paresis.

Recurrent laryngeal neuropathy is a condition in which affected horses make a

characteristic whistling or roaring sound due to obstruction of inhaled air as it passes through
the larynx. It occurs in Thoroughbreds, Warmbloods and draught horses over 16 hh and
rarely affects horses under 15.2 hh. It may be an inherited condition that is usually apparent

by the time the horse is 6 years old.

Structure and function of the larynx

The larynx (voice box) is situated in the horse’s throat at the top of the trachea (windpipe)
where it opens into the pharynx. It is made up of several cartilages and ligaments, joined in
such a way that it can open and close. The opening and closing of the larynx is controlled by

several small muscles. Most of these are innervated by the right and left recurrent laryngeal
nerves which run from the chest area along the trachea to the larynx.

NORMAL MOVEMENTS OF THE LARYNX

When the horse swallows, the larynx closes to prevent inhalation of food. During strenuous
exercise, the larynx opens fully to allow maximum air flow to the lungs. During respiration

while the horse is at rest, the larynx is in an intermediate position. It opens a little wider
during inspiration and narrows during expiration. In normal horses, the opening of the larynx

is symmetrical and the movement is smooth and equal on both sides.

Causes

For reasons that are not fully understood, the left recurrent laryngeal nerve undergoes