Understanding the Condition, What Causes It, and How to Manage It

If you’ve noticed your horse passing normal manure followed by watery liquid that soils the tail and hind legs, you’re not alone. This condition, known as free fecal water (FFW) or fecal water syndrome, is seen in horses across Australia and around the world. While it’s not usually life-threatening, it can be messy, irritating for the horse, and frustrating for owners to manage.

At Avon Ridge Equine Veterinary Services, we regularly help clients work through this tricky condition. In complex or chronic cases, our team can also offer advanced support through on-property consultations with our consulting internal medicine specialist, Professor Guy Lester. In this article, we’ll explain what FFW is, what causes it, and how you can manage it—with guidance on when it’s time to involve a veterinarian.

What is Free Fecal Water?

Free fecal water (FFW) is a condition where horses pass normal, formed manure balls followed by liquid water from the rectum. This watery discharge can happen before, during, or just after defecation. It’s different from diarrhea because the actual manure looks normal—it’s just the extra liquid that’s abnormal.

Common signs of FFW include:

• Wetting or soiling of the tail, hindlegs, and rump

• Irritation or skin scalding around the dock and thighs

• A sour smell or staining of rugs

• Discomfort during defecation, in some cases

Although most horses remain bright, eating, and healthy in themselves, the condition can impact their comfort, skin health, and even performance.

What Causes FFW?

There is no single cause of FFW. Instead, it’s thought to result from a combination of factors that affect how the large intestine (hindgut) absorbs water and separates digesta. Here are the main culprits:

1. Gut Motility and Water Absorption

Disruption to how the colon moves and reabsorbs water may cause liquid to remain separated from formed manure.

2. Gut Microbiome Imbalance (Dysbiosis)

Horses with FFW often have changes in their hindgut bacteria, which can influence digestion and water retention.

3. Diet and Forage Type

Stalky or poor-quality hay, sudden feed changes, or feeding haylage/silage can upset the digestive system and lead to FFW.

4. Stress and Behavioural Factors

Horses are sensitive to changes in routine, social hierarchy, and environment. These stressors may influence gut motility and water balance.

5. Dental Issues and Age

Older horses and those with dental wear may not chew fibre effectively, leading to fermentation issues and water separation.

6. Mild Gut Inflammation

While not common, some horses may have low-grade inflammation or increased gut permeability that interferes with water reabsorption.

When to Call Your Vet

While many cases of FFW are mild, it’s essential to rule out more serious causes of abnormal fecal consistency—especially if your horse:

• Shows signs of colic, discomfort, or lethargy

• Loses weight or condition

• Has worsening or continuous fecal water

• Has abnormal or soft manure alongside the water

• Doesn’t respond to feeding or management changes

At Avon Ridge Equine Veterinary Services, we offer full on-property workups for horses with FFW. This includes:

• Physical exam and dental assessment

• Faecal testing and parasite checks

• Dietary review

• Abdominal ultrasound and x-rays, which can be done easily on-site to assess gut motility, wall thickness, and check for sand or other abnormalities

Complex or Chronic Cases?

For difficult or persistent cases, we offer consultations with Professor Guy Lester, an internationally recognised equine internal medicine. Prof Lester brings decades of experience in equine gastrointestinal health and can visit your property to provide advanced diagnostics and help tailor a management plan for your horse.

Whether it’s identifying subtle causes of inflammation, interpreting ultrasound findings, or trialling newer treatments, Prof Lester’s expertise gives you access to specialist care without needing to travel to a referral hospital.

Management Strategies That Work

Managing FFW takes time and often involves trying a few different strategies. Here’s what we recommend:

1. Feed High-Quality, Soft Hay

• Use fine-stemmed, grassy hay

• Soak hay to reduce sugar and improve digestibility

2. Eliminate Feed Triggers

• Remove feeds high in molasses or fat

• Trial removal of lucerne or other legumes if suspected to contribute

3. Support the Gut

• Psyllium husk may help with water binding and sand clearance

• Use caution with clay or charcoal supplements—always speak with your vet first

4. Address Stress

• Maintain routine and paddock stability

• Provide social contact

• Avoid unnecessary changes to housing or companions

5. Advanced Therapies (e.g. FMT)

Faecal microbiota transplant has shown promise in some horses with chronic FFW. If suitable, Prof Lester can discuss and supervise this treatment during your consultation.

Long-Term Outlook

With a consistent approach and veterinary support, most horses with FFW can be managed successfully. However, some horses may have recurring episodes linked to stress, age, or environmental changes. It’s important to maintain regular dental care, avoid abrupt dietary changes, and involve your vet early if problems persist.

Need Help with a Case of Free Fecal Water?

We’re here to support you. Whether it’s a one-off consultation, full diagnostic workup, or a specialist visit for a chronic case, Avon Ridge Equine Veterinary Services offers the complete care your horse needs—right at your property.

Our services include:

• Field diagnosis and abdominal ultrasound

• Personalised feeding and management plans

• Access to internal medicine specialist Professor Guy Lester

• Ongoing case support and follow-up