Diarrhoea in foals

Diarrhoea is commonly seen in foals and can range from being relatively harmless to fatal. Knowing when and how to intervene can make all the difference.

When should I worry if my foal has diarrhoea?

If any foal has diarrhoea, it should be very closely monitored and veterinary advice should be sought promptly if there is any concern. Foals can deteriorate quickly, and it is always best to act early. Often the severity of the diarrhoea and the need for more intensive treatment is dependent on the age of the foal – with younger foals being more susceptible.

What is foal heat diarrhoea?

Foal heat diarrhoea is commonly seen in foals aged 4–14 days old, with affected animals often developing mild, self-limiting diarrhoea during this time. This coincides with the mare’s first season after foaling, hence the name “foal heat diarrhoea.” However, the diarrhoea is not actually linked to the mare’s hormonal changes but rather alterations in the foal’s intestinal microbial flora and diet as it begins to eat small amounts of forage.

Foals with foal heat diarrhoea remain active and alert and have a normal appetite. Their vital signs remain normal and faeces are semi-formed to watery and not particularly smelly. Close monitoring is essential to ensure the foal’s condition does not deteriorate but specific veterinary treatment is usually not necessary. The application of a protectant to the skin around the perineum helps prevent scalding of the buttocks.

What are other causes of diarrhoea in foals?

  • Bacteria
  • Viruses
  • Incorrect nutrition
  • Parasites

Bacterial diarrhoea

Common causative bacteria include Salmonella, Escherichia coli and Clostridium species. Rhodococcus equi is primarily a respiratory disease but can also cause diarrhoea in foals.

Depending on the age and immune status of the foal, causative agents involved, and extent of the infection, bacterial diarrhoea can be fatal. Veterinary intervention is essential and often intensive treatment is required, including antimicrobial treatment, correction of fluid loss and electrolyte abnormalities, and nursing care. Hospitalisation is often needed, especially in younger foals.

Diarrhoea is one of the most common signs of neonatal septicaemia and can be seen with any severe, systemic bacterial infection. These foals require intensive nursing and treatment.

Viral diarrhoea

Rotavirus is one of the most common causes of infectious diarrhoea in foals. Foals with rotavirus diarrhoea are usually very sick, depressed, and not nursing. They have profuse, watery and very smelly diarrhoea and are at risk of quicky becoming dehydrated. It is usually seen in foals that are 2 days to 6 months old and affected foals are highly contagious, so should be isolated. The diarrhoea usually lasts for up to seven days, although it can persist for several weeks. Treatment is generally supportive and involves giving intravenous fluids to prevent dehydration. Vaccinating the mare during pregnancy can help protect foals from rotavirus.

Nutritional diarrhoea

Nutritional diarrhoea can result from overfeeding or improper nutrition. This can happen if a foal is reunited with the mare after a period of separation, and with very greedy foals. When feeding orphan foals, it is important to use an appropriate milk replacer. Do not use cow’s milk. Nutritional diarrhoea can also develop when foals consume indigestible substances such as roughage, sand, and dirt.


Diarrhoea in foals has also been reported to be associated with parasites, such as Strongyloides westeri, Parascaris equorum, and Cryptosporidium species. Be aware of pasture rotation and have a well-structured worming regimen.

What should I do if a foal has diarrhoea?

Monitor the foal closely and contact your vet if you are concerned – foals can deteriorate quickly.

It is pertinent in all cases of foal diarrhoea to ensure excellent standards of hygiene, especially on studs, and isolation is recommended. Nominate who is responsible for the foal and reduce all unnecessary foot traffic. Anybody coming into contact with a foal with diarrhoea should wear disposable gloves and washable boots, with a disinfectant footbath outside the stable door. When the foal is back to full health and able to rejoin the herd, it is important to disinfect the stable thoroughly with an appropriate disinfectant.

All cases of diarrhoea result in increased fluid and electrolyte loss from the body. Replacement of these lost fluids and electrolytes is essential to prevent dehydration. In mild cases, where the foal is lively and still suckling, continued milk and water intake will help replace lost fluids. An oral electrolyte replacement treatment can help maintain fluid balance, although always speak to your vet first. Atta-Sorb gel and Kao-Sorb are specially formulated oral electrolyte replacement supplements, with added binding agents to help support foals through periods of digestive upset. They are easily administered and absorbed by foals with diarrhoea to help maintain their fluid and electrolyte balance. Friska Foal can help to support foals recovering from diarrhoea, with key vitamins and a prebiotic to support general and digestive health.

A foal with severe diarrhoea, that is not drinking or has an elevated temperature should be examined by a veterinary surgeon urgently.


Can I prevent foal diarrhoea?

Foal heat diarrhoea isn’t preventable but there are steps you can take to try and reduce the risk of the more severe causes. Ensuring all foals get a good amount of colostrum is vital for their immune system; foals who don’t are more susceptible to infections. Read more about feeding young foals here.

It is vital to monitor all foals very carefully during the foaling season so you identify cases of diarrhoea early – you can then act accordingly. Good hygiene throughout the season can also help minimise the risk of the infectious causes of diarrhoea.

Contact our equine experts if you need any advice on supplements that can help to support your mare and foal through the breeding season.

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