The term impaction refers to a blockage within the horse’s gastrointestinal tract. It is usually caused by a build-up of solid material, usually food or partially formed faeces, which prevents the normal passage of gut contents.
What triggers impaction?
The following factors may cause impaction in an otherwise healthy animal:
- A change in management, such as stabling a horse that was living out at grass
- A drop in the amount of exercise a horse gets, for example box rest after an injury
- Dehydration, due to insufficient fresh water
- Bingeing, such as when a greedy pony gains access to the feed room or an unlimited supply of hay or haylage
- Animals that eat straw bedding are also at risk
- A horse which eats unsoaked sugar beet may develop impaction of the oesophagus (choke)
- Animals grazing on sandy soil may take in sufficient quantities of sand to cause impaction of the colon
Impactions can also occur as a result of other conditions, such as dental problems, disease which reduce gut mobility, repeated sedation of the horse and severe roundworm infestation, particularly in youngsters.
Signs to look out for
Symptoms vary according to the severity and location of the impaction. In early cases of colon impaction, you may notice your horse is passing fewer droppings than normal and that the faecal balls are small, firm and dry. He may also be quieter than normal or refuse feed. As the impaction worsens the horse will show signs of colic, including pawing the ground, kicking at his belly, look round at his flanks, sweating, rapid breathing, lying down and rolling.
If your horse is showing signs of colic, call your vet immediately. While waiting for the vet to arrive, walk your horse around gently, on grass or another soft surface, if possible, so that he will not hurt himself if he rolls.
Do not let him eat. If he is determined to roll, then let him – it is almost impossible to stop a horse that really wants to roll and you could be injured when trying to do so. Do not administer any laxatives such as liquid paraffin before the vet has examined him.
If your vet diagnoses a colon impaction, he will probably administer a combination of water and laxatives by nasogastric tube. Liquid paraffin is often given to soften and lubricate the faeces. Magnesium sulphate solution (Epsom salts) is another commonly used laxative, which acts by drawing water back into the gut.
Painkillers, such as phenylbutazone (bute), will be given intravenously to control the discomfort until the impaction is passed. The horse must be starved and monitored to observe colic signs and amount of faeces produced.
He should be walked in-hand regularly to stimulate gut motility. Your vet may need to re-examine the horse several times to check the impaction is softening and to administer more laxatives and painkillers if necessary. Once the horse is comfortable and is passing droppings again, small amounts of laxative feed, such as grass and sloppy bran mashes, may be given, building back up to normal feed in a few days.
In severe cases of colon impaction, more frequent dosing of water and laxatives by stomach tube is needed, and the horse may need a drip, which requires hospitalisation.
In these cases, it can take days for an impaction to clear.
Impactions of the small intestine are more likely to require surgery. These tend to be caused by the horse eating inappropriate foodstuffs, such as twigs or shavings. Your vet may suspect a small intestinal obstruction if he or she can feel loops of small intestine that have become distended with gas and fluid during a rectal examination.
If any impaction is untreated, the horse will become more distressed and could even die due to severe shock or a ruptured bowel. Without a vet it is impossible to know whether colic is the result of an impaction, impending diarrhoea or a twisted gut, so colic must be treated as an emergency. However, most impactions are treated successfully and horses usually make a full recovery.
- For stabled horses in particular, try to feed little and often as far as possible, and include plenty of roughage in the diet
- Soaking hay is a good way to ensure that the horse gets plenty of moisture, and hard feed should also be wetted down
- If your horse does not tend to drink very much, introducing a salt lick or adding a teaspoon of salt to his feed can help
- Try to leave horses that are prone to impaction out at grass as much as possible
- Regular exercise is a very important way to prevent impaction. If your horse cannot be turned out to graze, make sure he has some form of exercise daily, even if it is just walking in-hand
- Horses or ponies that eat straw should be kept on an alternative bedding, such as paper or rubber matting