Free Fecal Water Syndrome in Horses

Updated April 12, 2024 | By: Andris J. Kaneps, DVM, PhD, DACVS, DACVSR

Free Fecal Water (FFW) syndrome is a condition where a horse passes fecal liquid separately from normal, solid manure. This can happen before, during, after, or completely independently of defecation and is considered a separate condition from diarrhea or loose stool.

Depending on the area in which you live, this condition may be called either Fecal Water Syndrome, Free Fecal Water Syndrome, or Free Fecal Liquid.

Ask the Vet Video on Fecal Water Syndrome

Watch as Dr. Lydia Gray discusses research studies on FFW and how it differs from episodes of diarrhea.

Impacts on Quality of Life

FFW is believed to be fairly common and mainly a cosmetic problem for horse owners as the hind legs and tail are chronically wet and filthy. However, horses that continually have feces and fecal water running down their back legs can be prone to developing irritating skin lesions.

Causes of Free Fecal Water Syndrome in Horses

Runny poop coming out of a paint horse that stains the back legs

Many potential causes of FFW have been investigated by veterinarians and researchers, but no clear underlying cause has been identified yet.

Two studies that compared the bacterial population in the gut (microbiome) of horses with free fecal water to healthy, unaffected horses showed no substantial differences between the groups [1, 2].

FFW has not been linked with infectious causes of diarrhea (like Equine Coronavirus or Salmonella).

A group of researchers in Germany explored some of the proposed theories on causes and discovered that neither dental disease nor a heavy parasite burden seemed to be associated with FFW [3].

However, FFW was found to be more likely to happen:

  • in horses of low rank or “pecking order” in the social hierarchy of a herd
  • in winter when subordinate horses were confined to a smaller space, leading to anxiety
  • in geldings versus mares (usually more dominant than geldings)
  • in paint horses

More studies are needed to examine the role of stress, nutrition, and other factors in the development and management of FFW.

Veterinary Diagnostics

When your horse’s manure is not their norm, it’s a good idea to involve your veterinarian.

Most vets approach the diagnosis of a horse with FFW similar to one with diarrhea or loose stool. That is, they start by taking a thorough history from the owner. Then they perform a complete physical examination with special emphasis on the digestive system. Finally, your vet may recommend specific tests to evaluate the overall health of your horse and the GI tract.

It can be helpful to confirm the presence of soiled hind limbs and tail as well as dirty stall walls and bedding. While on the farm, your vet may want to walk through the regular feeding and management programs, including turnout and herd status.

Treatment and Management of Free Fecal Water Syndrome

A group of three horses grazing on grass, two of them paint horses, and one a chestnut colored horse.

There is no standard treatment or set of recommendations for the care and feeding of horse suffering from FFW. Still, all potential causes for disruption in the GI tract should be addressed, including social stress.

FFW treatment could include:

  • Changing or reducing the size of the turnout group.
  • Making gradual adjustments to the diet (with the input of your vet and/or nutritionist).
  • Testing the effects of various medications and supplements one at a time on the passage of fecal water (again, in consultation with your vet).

Some horses seem to respond to less “bulk” or long-stem forage in the diet, to adding omega 3 fatty acids for a normal inflammatory response in the gut, and to the stabilizing effects of baker’s yeast or Saccharomyces cerevisiae.

At the same time, it is important to keep the skin on the hindquarters clean and dry to prevent sores. Your vet may have practical suggestions for keeping the skin healthy. Blanketing tips for colder months, fly management in warmer times, and products to clean and coat the tail and back legs (like petroleum jelly) may be suggested.

Key Takeaways

It can be frustrating to constantly be cleaning up soiled spots on your horse’s backend. It’s important to take action when you notice changes in your horse’s manure (whether the frequency, consistency, or color) and speak with your vet for an accurate diagnosis and treatment plan.

Evidence-Based References

  1. Schoster, Angelika, et al. “Dysbiosis Is Not Present in Horses With Fecal Water Syndrome When Compared to Controls in Spring and Autumn.” Journal of Veterinary Internal Medicine, vol. 34, no. 4, June 2020, pp. 1614–21.
  2. Laustsen, Louise, et al. “Free Faecal Water: Analysis of Horse Faecal Microbiota and the Impact of Faecal Microbial Transplantation on Symptom Severity.” Animals, vol. 11, no. 10, Sept. 2021, p. 2776.
  3. Kienzle, Ellen, et al. “Field Study on Risk Factors for Free Fecal Water in Pleasure Horses.” Journal of Equine Veterinary Science, vol. 44, Sept. 2016, pp. 32–36.

SmartPak strongly encourages you to consult your veterinarian regarding specific questions about your horse's health. This information is not intended to diagnose or treat any disease, and is purely educational.