Intestinal stones in horses

These are formed by an accumulation of minerals around foreign objects in a horse’s gut, and if left to grow too large, can be highly dangerous.

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“Good grief, how did my horse manage to swallow such a huge stone?” This is a common reaction on seeing an intestinal stone, also called an enterolith, for the first time.

An enterolith is a concretion of magnesium ammonium phosphate salts, also called struvite, formed in a horses’ colon. It is caused by swallowing a foreign object such as gravel, shavings, baling wire or even a bottle top.

The uneven surfaces of the object may allow it to become lodged against the colon wall, producing an irritation, and minerals then accumulate around the object.

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The process is similar to that of a pearl in an oyster. The stones can be round or tetrahedral, and weigh up to 7kg. Smaller stones generally cause no problems and are sometimes passed in the droppings, but larger ones can cause blockages and severe colic.

Horses between five and 10 years of age are most likely to be affected, and there is a high incidence in Arabs, predominantly mares. Horses that drink out of boreholes with high mineral deposits or that eat too much lucerne are also more prone to enteroliths.

Lucerne provides large amounts of magnesium and phosphorus, which tend to alkalise the gut. This high alkalinity allows the minerals to precipitate and attach to any foreign bodies in the gut.

Nearly all horses with enteroliths are found to have a diet that consists of at least 50% lucerne. Foreign objects in a paddock can be a problem too. It is essential to keep this area clean and neat.

Unfortunately, there are no specific symptoms of the problem. But intermittent colic, distended flanks or mucous-covered faeces could possibly indicate a stone. Contact your vet at any sign of colic – even if you think the pain is mild!

Bear in mind, however, that the stones are usually out of reach of a rectal examination, and that surgery is the most accurate method of diagnosing an enterolith.

It’s expensive, too. The horse is placed under general anaesthesia, the stone is removed and the intestines thoroughly lavaged, or cleaned.

If there are no complications, the prognosis is usually very good. But if your stable management is not addressed, there could be a reoccurrence, and this will inevitably be much more serious.

Prevention is always better than cure. Here are some tips:
• Decrease lucerne intake to less than 50% of the horse’s ration. Include grass and oats hay.
• Do not feed bran exclusively.
• Increase the hard concentration of hay to decrease the pH of the intestinal tract.
• Add one cup of apple cider vinegar to one feed every day.
• Ensure that your horse grazes for a few hours every day. Or break up the concentrate feeds into six “servings” a day.
• Exercise your horse regularly. Prolonged stabling decreases the movement of food through the digestive tract.

Contact Kim Dyson on 082 888 6511.