Windsucking is a stereotypical behaviour (also known as a stable vice). Stereotypical behaviours or stereotypies are described as repetitive behaviours which have no apparent function.
Windsucking is the inspiration of air and is performed by a horse creating a vacuum in the mouth and swallowing the air whilst arching the neck. It is closely associated with crib biting but it is thought to be worse as the horse does not grasp on a fixed object.
When high-grain diets are fed it stimulates endorphin release which in turn causes dopamine to be released. Windsucking is then performed to mimic the dopamine release. Other than a grunting noise and the hypertrophy of muscles on the underside of the neck there are no real adverse side effects. It becomes a habit as dopamine is released into the blood stream when a horse is windsucking. Horses can very quickly become addicted to this dopamine release.
Recently there have been links made between gastric ulcers and windsucking. It is thought that horses with gastric ulcers seek the dopamine release which is associated with eating as they desperately want to buffer the stomach acid.
Once a horse starts windsucking it is very hard to stop as a habit will have formed. Helping to maintain a healthy gut is the main objective with a windsucking horse. It is therefore important to minimise the risk of gastric ulcers so that they do not become worse. The best way is to increase the horses forage intake and chewing time as chewing stimulates saliva release. Saliva contains bicarbonate which buffers the stomach acid so that ulcers do not form. Ideally horses should be fed ad lib hay so that there is no risk of gastric ulcers. If an animal is overweight the hay can be soaked so that it contains very few nutrients as long as a broad spectrum vitamins and minerals supplement is being fed.