Choke is a condition in horses in which theesophagus is blocked, usually by food material. Although the horse is still able to breathe, it is unable to swallow, and may become severelydehydrated. A secondary condition,aspiration pneumonia, may also develop if food material and saliva accumulate in thepharynx, spilling into thetrachea and into the lungs. Choke is one of the "top 10" emergencies received by equineveterinarians.^[1]

The condition is seen in otherEquidae likemules anddonkeys.

Chewing: Horses may develop choke if they do not chew their food properly. Therefore, horses with dental problems (e.g. acquired or congenitalmalocclusion, loose or missing teeth, or excessively sharp dental ridges) that do not allow them to completely grind their food are particularly at risk.^[2][3] In addition, horses thatbolt their feed and do not take the time to chew properly are more likely to suffer from choke.^[4][5]

Dry Food: Dry foods may cause choke, especially if the horse does not have free access to water, or if the horse has other risk factors linked to choking.^[4] While pelleted or cubed feeds in general fall in this category, horse owners sometimes express particular concerns aboutbeet pulp. However, while horses have choked on beet pulp, a university study did not document that beet pulp is a particular problem.^[4] It is believed that choke related to beet pulp is linked to the particle size and the horse's aggressive feeding behaviour, rather than the actual feed itself.^[5] Research suggests that horses that bolt their feed without sufficient chewing, or who do not have adequate access to water, are far more likely to choke, regardless of the type of feed, compared to horses that eat at a more leisurely rate.^[5] The risk of choke associated with any dry feed can be reduced by soaking the ration prior to feeding.^[4]

Foreign Objects: Horse may ingest non-edible materials such as pieces of wood.Cribbers may be more prone to this type of choke, if they happen to swallow a piece of wood or other material while cribbing.

• Difficulty swallowing (horse may try to swallow without success)
• Lack of interest in food
• Coughing
• Extending the neck and head, usually in a downward direction
• Discharge from the nostrils. usually green in color, although it may also be yellow or clear, often looks likevomit
• Increasedsalivation, saliva drooling from the mouth
• Heart rate may increase slightly, due to thedistress of the animal
• Occasionally, a lump on the side of the neck is visible or can bepalpated, where the esophagus is blocked. This is normally most obvious on the left.

If a horse is suspected of choke, aveterinarian will often pass a stomach tube down the animal's esophagus to determine if there is a blockage. Failure to access thestomach with the tube indicates a complete obstruction; difficulty passing the tube may represent astenosis, or narrowing; or a partial obstruction.Radiography andendoscopy are also used in refractory cases.

Choking horses should be deprived of food and drink pendingveterinary attention, so as not to increase the obstructive load within the esophagus. The veterinarian will oftensedate the horse and administerspasmolytics, such asbutylscopolamine, to help the esophagus to relax. Once the muscles of the esophagus no longer force the food down the throat (activeperistalsis), it may slip down on its own accord. If spasmolytics do not solve the problem, the veterinarian will usually pass a stomach tube through one of the nostrils and direct it into the esophagus until the material is reached, at which pointgentle pressure is applied to manually push the material down. Gentle warm waterlavage (water sent through the stomach tube, to soften the food material) may be required to help the obstructing matter pass more easily, but caution should be exercised to prevent further aspiration of fluid into the trachea.

Refractory cases are sometimes anesthetised, with an orotracheal tube placed to prevent further aspiration and to allow for more vigorous lavage. Disruption of the impacted material can sometimes be achieved via endoscopy. If these methods still do not lead to results, the horse may requiresurgery to remove the material.Some workers have advocated the use ofoxytocin in choke, on the grounds that it decreases theesophageal muscular tone.^[6] However, this technique is not suitable in pregnant mares, as it may lead toabortion.

After the material has passed, a veterinarian may try to prevent the onset ofaspiration pneumonia by placing the horse onbroad-spectrum antibiotics. The animal should be monitored for several days to ensure that it does not develop pneumonia, caused by inhalation ofbacteria-rich food material into thelungs.

The material caught in a horse's throat usually causesinflammation, which may later lead toscarring. Scarring reduces the diameter of the esophagus (astenosis orstricture), which increases the chance that the horse may choke again. The veterinarian may therefore place the horse on a course ofNSAIDs, to help to control the inflammation of the esophagus.

Often the horse will only be fed softened food for a few days, allowing the esophagus to heal, before it is allowed to gradually resume its normal diet (e.g. hay and unsoaked grain). Horses with re-occurring chokes may require their diet to be changed.

• Always provide water for the horse
• Soak dry foods before feeding to horses prone to choke
• Change feeds gradually
• Discourage the bolting of food: spread out feed, place large, flat stones (large enough so that the horse can not swallow it) or salt blocks in the feed bin so that the horse must slow down, or feed smaller meals more often
• Cut apples, carrots, or other treats into small pieces
• Withhold feed material for one hour following sedation

• RJ Rose; DR Hodgson (2000).Manual of Equine Practice. WB Saunders. pp. 309–312.
• PT Colahan; IG Mayhew; AM Merritt; JN Moore (1999).Manual of Equine Medicine and Surgery. Mosby Ltd. pp. 198–199.