Have you noticed that your horse’s stall walls or bedding seem dirtier than normal? Are their tail and hind legs constantly stained? Do you find yourself frequently bathing them to remove these stains?

If you have observed any of these signs, it could be a result of Free Fecal Water Syndrome (FFWS).

Free Fecal Water Syndrome often goes undiagnosed by horse owners. In some cases, a stained tail or hind leg is explained as the horse being “messy” or because they “must have rolled in their stall overnight”.

FFWS is a topic on the rise within the equine research community as the prevalence and awareness of this condition grow. More horse owners are discussing the struggle they face to ensure proper care and welfare for horses with FFWS.

According to veterinarians, this condition is fairly common in horses but very little is known about the causes. There is also limited scientific information available on the proper treatment of FFWS. Most of what we known about how to resolve FFWS comes from anecdotal case reports as opposed to clinical studies.

This article will guide you through what free fecal water syndrome is, its diagnosis, common symptoms, potential causes, and possible treatments that may aid in the reduction or elimination of this condition.

If you suspect your horse is dealing with free fecal water, submit their diet for analysis online and our equine nutritionists can review and help you make changes to better support your horse’s digestive health.

What is Free Fecal Water Syndrome?

Free fecal water syndrome is a condition in which horses experience both solid and liquid phases during defecation. The liquid phase can occur before, during, or after defecation of the solid phase or sometimes occur completely separate from the solid phase. [1][2][3][4][5]

In simpler terms, free fecal water syndrome occurs when the horse releases solid feces, and either before, during, or after this, free water runs out of the anus.

From what is known about free fecal liquid in horses, there appears to be no threat to general health associated with this condition but it does become a constant maintenance issue for owners.

The liquid phase of defecation can cause stains on the area around the anus, hind legs, and tail of the horse. This may require routine washing which has been shown to result in skin irritations and inflammation of these areas. [1][2][3][4][5]

This condition may last a few days, months, or years and may change in severity over time. FFWS is has only fairly recently been given its name; however, it is believed to be a reasonably common occurrence. [1]

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Fecal Water Syndrome Diagnosis

Veterinarians approach the diagnosis of FFWS in horses similarly to how they would approach diagnosing diarrhea. However, determining whether a horse has FFWS or diarrhea can be difficult.

Veterinarians usually begin their examination by first learning as much about the horse’s history as possible, asking for details such as: [1]

  • Age, breed, and existing gastrointestinal issues
  • Current feeding program
  • Horse’s daily schedule
  • Any changes in horse’s routine (exercise regimen, turnout times, herd, diet)
  • Stress/anxiety level

Horses that are affected by FFWS usually look healthy and seem to be in good body condition and overall health status. This makes diagnosis a challenge for both veterinarians and horse owners.

Common Symptoms of Free Fecal Water

Free fecal water syndrome appears to be more of a cosmetic and maintenance issue rather than a severe health issue but may signify broader dietary and/or welfare issues. Due to this, symptoms or signs that a horse may be affected by FFWS are usually overlooked.

Some common signs that your horse may have FFWS include: [1][2][3][4][5]

  • Fecal matter soaked on the hind legs, tail and around the anus
  • Increased need to wash areas around the anus, hind legs and anywhere that may have liquid phase fecal matter stains
  • Irritation or skin lesions on areas that require increased washing due to staining from fecal water
  • Dermatitis around the hind legs, dock, or area around the anus
  • Signs of discomfort when defecating feces
  • Extensive tail swishing after defecation
  • Nervous trampling of hind legs after defecation
  • Stall walls and bedding frequently dirty with fecal water
  • Abdominal bloating

Causes of Free Fecal Water Syndrome

There is limited research available on free fecal water syndrome. The true causes, prevalence, and frequency of association with other conditions still require investigation.

It has been suggested that the cause of FFWS includes both internal and external factors. Suggested internal factors include:

Diet Imbalances

In horses, it is essential to make sure the proper type of feed is provided and that is it being fed in the proper amounts. The type of food your horse ingests is largely responsible for how stable his or her fecal material will be.

Diets with high inclusion of concentrates have been reported to cause changes to the characteristics of feces. Concentrates include ingredients such as oats, barley, maize, and bran or commercially made extruded or pelleted feeds.

Horses fed hay with excessive amounts of oats have been found to produce stools that are less well-formed. However, these horses were fed an extremely high amount of oats (4.55 kg / 10 lb) twice per day. It is unclear if more commonly fed amounts influence manure quality. Increased FFW was not reported and their colonic contents lacked the low viscosity free water phase found in horses fed hay only. [9]

Veterinary case reports suggest that many cases of FFWS are reduced or eliminated by implementing dietary changes. [1][9]

Switching the type of forage, changing the feeding schedule, and avoiding excess water-soluble carbohydrates (fructans and sugars) might reduce FFW. [9]


Another factor believed to contribute to FFWS is dysbiosis, generally defined as an imbalance in the gut bacteria.

Dysbiosis occurs when there is an imbalance in the bacterial colonies that make up the horse’s gastrointestinal tract. Normally dominant species of bacteria (such as those found in equine probiotics) are out-competed by other species or there is a decrease in the number or diversity of organisms.

Dysbiosis can have a number of causes including stress, age, dietary changes, or use of antibiotics. In horses, dysbiosis can be a component of FFWS, diarrhea, colic, colitis, leaky gut syndrome, gastric ulcers and other digestive health problems. [1][7]

The number and diversity of microorganisms, and therefore the ability to easily adapt to diet changes, is markedly decreased in older horses, putting them a greater risk of digestive dysfunction. [6]

Horses are hindgut fermenters that house a complex and diverse set of microorganisms (bacteria, yeast protozoa, fungi) within the gastrointestinal tract that help them to process large quantities of plant fibers. Fibre fermentation can provide up to 70% of your horse’s energy in the form of volatile fatty acids (VFAs). Absorption of VFAs, along with sodium and bicarbonate, is required for normal water absorption in the colon. [8]

The gastrointestinal tract of horses is completely reliant on the balance of these microorganisms to be able to perform and maintain proper digestion.

The causes of dysbiosis can include sudden ch