Why does my horse have diarrhoea?

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.