Choke (horse)

Choke is a condition in horses in which the esophagus is blocked, usually by food material. Although the horse is still able to breathe, it is unable to swallow, and may become severely dehydrated. A secondary condition, aspiration pneumonia, may also develop if the food material travels up through the nasal passageway and down the trachea into the lungs. Choke is one of the "top 10" emergencies received by equine veterinarians.^[1]

Additional recommended knowledge

Daily Visual Balance Check

How to quickly check pipettes?

Don't let static charges disrupt your weighing accuracy

Causes

Chewing: Horses may develop choke if they do not chew their food properly. Therefore, horses with dental problems (e.g. acquired or congenital malocclusion, 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 that swallow large pieces of food (such as large carrot or apple slices), or greedy animals that do not take the time to chew properly may suffer from choke.

Dry Food: Choke may occur when unsoaked beet pulp is fed, as the sugar beet will absorb water as it goes down the esophagus, and expand. Although this is not invariably the case - some horses seem able to cope adequately,^[4] - great caution should be exercised. Other dry foods may cause choke if the horse does not have free access to water.

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.

Signs of Choke

• Difficulty swallowing (horse may try to swallow without success)
• Disinterest 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 like vomit
• Increased salivation, saliva drooling from the mouth
• Heart rate may increase slightly, due to the distress of the animal
• Occasionally, a lump on the side of the neck is visible or can be palpated, where the esophagus is blocked. This is normally most obvious on the left.

Diagnosing Choke

If a horse is suspected of choke, a veterinarian will often pass a stomach tube down the animal's esophagus to determine if there is a blockage. Failure to access the stomach with the tube indicates a complete obstruction; difficulty passing the tube may represent a stenosis, or narrowing; or a partial obstruction. Radiography may also be used as a last resort.

Treatment

Choking horses should be deprived of food and drink pending veterinary attention, so as not to increase the obstructive load within the esophagus. The veterinarian will often sedate the horse and administer spasmolytics, such as butylscopolamine, to help the esophagus to relax. Once the muscles of the esophagus no longer force the food down the throat (active peristalsis), 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 point gentle pressure is applied to manually push the material down. Warm water lavage (water sent through the stomach tube, to soften the food material) may be required to help the obstructing matter pass more easily. If these methods still do not lead to results, the horse may require surgery to remove the material. Some workers have advocated the use of oxytocin in choke, on the grounds that it decreases the esophageal muscular tone.^[5] However, this technique is not suitable in pregnant mares, as it may lead to abortion.

Following Up

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

The material caught in a horse's throat usually causes inflammation, which may later lead to scarring. Scarring reduces the diameter of the esophagus (a stenosis or stricture), which increases the chance that the horse may choke again. The veterinarian may therefore place the horse on a course of NSAIDs, to help the 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.

Prevention

"Prevention is better than cure".

• Always provide water for the horse
• Soak beet pulp before feeding
• 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

References

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