What is Choke in horses?

Choke is a condition in horses in which the oesophagus 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 food material and saliva accumulate in the pharynx, spilling into the trachea and into the lungs. Choke is one of the “top 10” emergencies seen by equine veterinarians.^[1]

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 bolt 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 about beet 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.

Signs of Choke

• 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 colour, 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 distressof the animal
• Occasionally, a lump on the side of the neck is visible or can be palpated, where the oesophagus 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 oesophagus 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 and endoscopy are also used in refractory cases.

Treatment

Choking horses should be deprived of food and drink pending veterinary attention, so as not to increase the obstructive load within the oesophagus. The veterinarian will often sedate the horse and administer spasmolytic, such as butyl scopolamine, to help the oesophagus to relax. Once the muscles of the oesophagus no longer force the food down the throat (active peristalsis), it may slip down on its own accord. If spasmolytic do not solve the problem, the veterinarian will usually pass a stomach tube through one of the nostrils and direct it into the oesophagus until the material is reached, at which point gentle pressure is applied to manually push the material down. Gentle 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, 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 require surgery to remove the material. Some workers have advocated the use of oxytocin in choke, because it decreases the oesophageal muscular tone.^[6] 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 oesophagus (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 to control the inflammation of the oesophagus.

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

Prevention

• 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 cannot 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

What causes colic in horses?

Sand colic is caused by the ingestion of sand by your horse. This occurs most commonly on sandy soils, when the availability of roughage is reduced, and some horses just seem to develop a liking for grazing low to the ground and even licking sand! In Western Australia, this is a particular problem due to the sandy nature of our soil. Sand is highly irritating to the intestines and is also much heavier than the normal material that horses eat. These two factors cause blockages and colic in horses, and diarrhoea.

What are the symptoms and signs of sand colic?

Many horses with a sand accumulation do not show symptoms until they suddenly develop either colic or diarrhoea. Colic symptoms mimic other forms of colic – lying down frequently, rolling, pawing, stretching and refusing to eat. This is caused by blockage and irritation of the intestine by the heavy sand burden. Horses can develop either chronic or acute diarrhoea from sand irritation, which can be very serious in nature.

How can I tell if my horse has a sand accumulation?

If your horse is kept on sand, and certainly if it grazes or is fed off of sand, it is highly likely they will have some degree of sand in the digestive tract. A simple test, that can easily be done at home, is to mix faeces with water and suspend in a disposable glove. If there is sand present, this will sink to the bottom of the fingers of the glove. It should be noted however that this test is not hugely accurate and can easily have “false negative” results, meaning that there is no sand seen but the horse still has a sand accumulation.

 

You can sometimes hear sand moving in the ventral abdomen if you listen with a stethoscope, but again this is not particularly accurate and it may not always be possible to detect sand this way.

A more sensitive test is to x-ray the horse’s abdomen to look for sand accumulation in the lower part of the abdomen. This not only identifies sand, but also allows us to score the amount of sand present and ascribe it a risk factor for the development of issues. For example, if a large burden is seen, we can be more cautious with monitoring and treatment.

How is sand colic treated?

Prevention is always better than cure – but that is easier said than done in sandy WA!

The feeding of psyllium is a common way to get rid of sand. This needs to be done for only a short period at a time, and the dose rate to be effective is quite high. Unfortunately, many horses do not find this palatable.

Most veterinarians recommend drenching with a purgative sand drench to remove any sand accumulations before they cause clinical signs. Drenching with psyllium can also be an option.

How can we help?

• Book a Sand Drench at the clinic
• Psyllium drench
• Sand x-rays (note, abdominal x-rays may not be suitable for every case. This can be discussed with the veterinarian at the time of consultation)
• Call the clinic as soon as possible  on 9296 3884 if you note any of the signs of sand colic in your horse