If your horse develops diarrhoea, it can understandably be a cause for concern. What has caused it, and how do you know whether the illness is serious? What do you do if your horse develops diarrhoea? We’ll explore these questions in this blog.

Causes of diarrhoea in horses

There is a wide variety of causes of diarrhoea in horses, which can be broadly summarised into several categories (although there is often overlap between them):

Infectious 

There are certain bacterial infections, such as Salmonella, that can cause sudden and often severe diarrhoea in horses. In these cases, a lot of fluid can be lost quickly, resulting in dehydration and added pressure on the heart and circulatory system. This type of diarrhoea (sometimes termed acute colitis) can be associated with signs of colic (abdominal pain). Some horses also develop laminitis, as a result of the build-up of toxins in the body. Diarrhoea of this nature requires prompt and aggressive treatment, and can easily be fatal if not treated rapidly.

Parasitic 

Intestinal worms are known to cause diarrhoea, as well as other abdominal issues such as colic and occasionally blockages of the gut. For example, small redworms (cyathastomes) can cause serious diarrhoea especially in young horses. 

Inflammatory 

Inflammatory bowel conditions can result in diarrhoea as well as weight loss or difficulty holding condition. 

Dietary 

A sudden change in the dietary regime can upset the delicate balance of bacteria in the gut, resulting in diarrhoea. Similarly, access to lush pasture or over-eating of cereals, such as when a horse breaks into the feed room, can cause sudden onset diarrhoea. In particular areas of the country with sandy soils, ‘sand colic’ and associated diarrhoea can be an issue. This may occur when horses are on poor-quality, sandy pasture with little supplementary feeding.

Cancers 

Bowel tumours can occur and result in diarrhoea and other signs, although these are fairly uncommon in horses.

Drugs or toxins 

Certain drugs can sometimes be a cause of diarrhoea. For example some horses can take an adverse reaction to phenylbutazone (‘bute’). Diarrhoea is also a known side effect of many antibiotic drugs. Of course sometimes your horse may need antibiotics to treat an infection; in this case your vet will be able to discuss any risks with you and signs to look out for. This is one reason why it is important that antibiotics are only given when really needed, and that your horse only receives antibiotics when they are prescribed by a vet at the correct dose for your horse.

What should I do if my horse has diarrhoea?

  • Firstly, bring your horse in off the grass into a stable and avoid contact with other horses in case the illness causing the diarrhoea is contagious.  
  • Contact your vet for advice; they will be able to determine from your description how urgently a visit is required. When your vet visits, they will perform a full examination including evaluating your horse’s hydration status and temperature. 
  • The vet will often need to take samples of dung to send to a laboratory to look for infectious agents. Because some bacteria such as Salmonella can be shed intermittently, they may need to take several samples over a few days to send away to give the best chance of detecting any infectious cause. 
  • Sometimes, it is not possible to know for certain about the cause of diarrhoea, but in serious cases it is often more crucial to focus efforts on administering life-saving treatment. 

Is there anything I can do to prevent diarrhoea?

Your vet will be happy to discuss aspects of prevention with you. Here are some points to consider:

  • Introduce dietary changes gradually & restrict access to lush pasture
  • Ensure your feed room is secure in case of any escapees!
  • Try to avoid or minimise causes of stress for your horse, such as long journeys. Although there isn’t conclusive evidence to support their use, some owners use a probiotic supplement (containing ‘good’ gut bacteria) around times of anticipated stress, which may help to keep your horse’s gut healthy.
  • Ensure your yard has a comprehensive worm control plan in place. This should encompass management strategies, such as poo-picking fields, as well as diagnostic tests such as worm egg counts. Wormer should only be administered when required (such as after a positive test result), not given routinely.

As we can see, there are steps you can take to reduce the risk of your horse developing diarrhoea, but sometimes it cannot be entirely prevented. In the event that your horse does develop diarrhoea, enlist your vet’s expert help with getting your horse well again.

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