Free Fecal Water Syndrome in Horses


Free fecal water syndrome (FFW) in horses refers to a condition where the horse passes watery or liquid feces without solid material. You will usually see a liquid stream before or after passing relatively normal manure. Occasionally, a horse might lift their tail and dribble some liquid without passing manure. FFW is different from diarrhea in horses and is not considered contagious or infectious diarrhea. However, your vet should determine that as the two conditions can look alike.


We all know that so many things can happen to horses that look alike, so getting your vet involved from the beginning is essential to rule out any possible dangers to your horse or the herd. And you want to ensure your horse is as comfortable as possible. 


horse hind end and tail chestnut horse

Ah, the oft-problematic business end of a horse.


Table of Contents: 


How does FFW impact the horse? 

What are the causes of free fecal water syndrome?

Types of forage and their role

Signs of FFW


How to treat FFW

Fecal transplants – it’s a thing! 

Grooming the horse with FFW


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How Does Fecal Water Syndrome Impact the Horse?


  • FFW creates a few problems for horses and horse owners. One, a horse might be uncomfortable or painful in their gut all the time or just when passing fluid. Luckily, most individual horses show no signs of gastrointestinal pain, while others may show colic signs, like strong gut contractions, belly kicking, social stress, and general irritation.


  • Then you have the problems of the messy tail and legs. This grooming challenge may be slightly less annoying in the summer when you can hose your horse, but the acidic nature of the fluid can scald the skin. Patches of hair loss and skin lesions on the hind legs often appear without intervention and might be susceptible to infections. 


  • A messy and stained tail also promotes tangles. Not to mention the terrible odors that attract flies, adding to your horse’s irritation. In colder weather, the wet skin and hair can put your horse at risk of frostbite. While rare, frostbite can happen in otherwise healthy horses. 


  • You will also spend excessive time cleaning blankets, leg straps, and grooming tools. Luckily, no one else at the barn will want to borrow your brushes.  


horse manure that is too runny

This is horse diarrhea – yes there is water, but the manure itself is also watery. 


What Causes Fecal Water Syndrome?


As with most horses, free fecal water syndrome in horses can be caused by various factors.


  • One of the most significant “umbrella” causes of FFW is dysbiosis. Dysbiosis is an imbalance of the normal microbial population in the gut, leading to an overgrowth of harmful bacteria and a decrease in beneficial bacteria – and it has many causes. 


  • One common cause is the overfeeding of lush, young grass, which can lead to an imbalance in the gut bacteria and excessive fermentation. This process is the same as when discussing those sugars and starches leading to laminitis and colic. 


  • When horses ingest large volumes of sugary feeds and pasture, the microbes in their hindgut have an absolute party. The by-product of that party is a change in gut pH, a die-off of microbes, and lots of microbe poop that leads to endotoxins. The disruptions in the hindgut allow those endotoxins to enter the bloodstream through the intestinal wall and right into the hooves, risking laminitis. The excessive gas in the hindgut after this microbe party contributes to colic. All of these complications can lead to free fecal water syndrome.  


manure on a fork

A horse with FFW will often have normal-looking manure piles. 


More possible causes


  • There’s also a group of general metabolic disorders like PPID (formerly Cushing’s) and insulin resistance that may influence FFW syndrome development. And if that’s not enough, it might also be due to changes in the hindgut’s flora caused by antibiotics or other medications. And would you believe that horses have malabsorption disorders that disrupt the normal absorption of water in the digestive process? 


  • And let’s not forget about internal parasites, like strongyles and tapeworms, that create traffic jams and steal nutrients from your horse’s digestive system. These jerky worms damage the intestinal lining, cause inflammation, and interrupt your horse’s digestive system’s normal functions, leading to increased manure fluid. 


  • Oh, and also stress! Travel, diet changes, training obstacles, and so many things that cause horses stress can impact their digestion. It’s also been noted that some horses at the lower end of the herds’ social structure are more likely to develop FFW. And allergies! Food allergies are real for some horses, and may not appear as hives or other typical allergic reactions.  


  • There’s also dental health to consider. Waves, hooks, abscesses, and other dental issues cause pain and reduce your horse’s ability to chew their food properly. Aside from being a choke risk, your horse won’t get enough chew time, which may impact the digestion of feeds and the rest of the food’s journey toward becoming manure. Poor dental health also contributes to an overall poor body condition.


bars and tongue of a horse's mouth

Regular dental care for horses is a must for healthy digestion. 


Forage Type


  • The forage type of grass and legume hays can significantly impact the occurrence of free fecal water syndrome in horses. Grass hays, such as timothy and bermudagrass, tend to have lower protein and sugar content than legume hays, like alfalfa and clover. Research shows horses fed high protein and higher sugar types of forages, often associated with legume hays, are more likely to develop FFW. This is logical, as the same situation applies to colic and laminitis. Thanks, party animal microbes!


  • Add to this the fiber content of long stem forage for horses – legume hays typically have lower fiber content and higher calcium and phosphorus levels than grass hays, which can lead to changes in the gut microbe balance and, therefore, increase the risk of FFW.


What are the signs of FFW in horses?


Here are some signs of FFW Syndrome in horses that you might see: 


  • Fluid accompanying manure passing, or just fluid passing at random times. It’s possible that diarrhea can happen, too. If your horse has diarrhea, you and your vet need to rule out any contagious conditions while exploring the possibility of FFW. Diarrhea can lead to dehydration and electrolyte imbalances, and if it’s contagious, every horse in the herd can come down with it.  


  • Skin irritation and inflammation around the anus, under the tail, and down the legs may be present due to the constant contact with free fecal water. It might be more challenging to see in dark-colored horses, and it can look like sweat in the summer. It might feel like sweat or water if you touch it, but it will likely have quite the aroma.  


  • Horses with FFW may have noticeable staining on their tail due to the constant dripping of fecal water. Dried fecal liquid can be smelly and sticky and create many tail tangles.  


  • Horses with FFW may show behavioral changes and exhibit signs of discomfort or agitation, such as tail-swishing or pawing at the ground. You and your vet should rule out colic, colitis, or other problems.  


  • Chronic FFW can lead to weight loss in horses, as the condition can affect their ability to absorb nutrients from their food properly. This is also indicative of parasites and metabolic disorders, so there is much to investigate and rule out. 


  • You might notice that changes in hay sources, switching bagged feeds, or moving to a new pasture trigger an episode of free fecal water syndrome.  


close up view of horse nose eating hay

Forage types can make a difference in gut health. 


Diagnostics for Free Fecal Water Syndrome


  • How does your vet diagnose Free Fecal Water Syndrome (FFW)? It’s a combination of physical examination and laboratory tests. Your vet should consider your horse’s overall condition, including its body score, hydration levels, and any signs of discomfort or pain. They may also check for signs of inflammation or irritation under the tail and any evidence left on the legs and tails. Ideally, your vet will witness your horse passing fluid. In today’s handheld computer age, you might be able to grab a video or snap some pics for your vet.


  • Your vet may want to send off a fecal sample to test for parasites, mucus, and blood in the feces, none of which are usually obvious to the naked eye. Also, you vet will likely run bloodwork like the complete blood count (CBC) to check for any signs of inflammation or infection in your horse’s body.


  • It’s also possible that X-rays, ultrasounds, or endoscopes can help narrow down potential causes. Some of these procedures may require going to an equine hospital, but many can be done in the field. 


How is FFW treated in horses?


Here are some treatments for free fecal water syndrome (FFW) in horses:


Dietary modifications:


  • I’ll preface this by saying you should make the small investment and talk to an Equine Nutritionist to work towards a more balanced diet. Find an actual PhD who can work with your vet to find support for your horse. Finding a good diet for a horse, especially one with FFW, is tricky, and you want expert help. 


  • You can implement changes in your horse’s diet, such as reducing the amount of high-sugar or high-starch feeds, increasing the amount of dry forage, and providing a balanced diet to promote gut health. Fiber pellets may help, too. Think of it as a laminitis diet, if you will, grass hays, low non-structural carbohydrates (NSC) value bagged feeds. Make any diet changes over several weeks. 


  • Using slow feeders is just about the most important thing you can do. And there are slow feeders for any feed you can imagine: bagged feeds, pellets, cubes, long-stem forage, and pasture. Grazing muzzles are a slow feeder that your horse wears. Adding water to horse’s feeds may help if there’s a risk of dehydration. 


  • Probiotics and prebiotics: These supplements can help to restore the balance of bacteria in the hindgut. Probiotics are live microorganisms – the beneficial gut bacteria – that compete with harmful bacteria in the hindgut of horses to help with digestion and boost the immune system. Prebiotics are the foods that good microbes need to thrive. When you feed pro- and prebiotics, you give your horse good microbes and the food those microbes eat. 


flax for horses Thank you!

Omega-3 fatty acids support gut health and give your horse’s coat that extra bloom. 


Omega-3 fatty acids


  • Current research suggests that the imbalance of omega-3 and omega-6 fatty acids in the horse’s diet may contribute to the development of FFW. Omega-3 fatty acids, found in sources such as flaxseed, chia, and fish oil, are known for their anti-inflammatory properties and ability to support a horse’s digestive health. When horses have a higher intake of omega-6 fatty acids than omega-3 fatty acids, it can lead to increased inflammation in the digestive tract (and elsewhere), potentially contributing to the onset of FFW.


  • Very often, a horse will not have enough Omega-3’s in their diet. Pasture is a good source, but it’s sometimes unavailable every season. Supplements are an easy (and delicious) way to add them in. Your horse will also shine like a newly minted coin, as Omega-3 boosts skin and coat health.  


  • Note – corn oils have long been a way to boost shine, but they are HIGH in omega-6 fatty acids and won’t do anything to help your horse except make them shiny. The goal is to have your horse eating more Omega-3’s than Omega-6’s. We don’t know the exact ratio, but it’s around four times as many. 


Hindgut buffers


  • These clever supplements help to negate the pH changes of the hindgut, keeping the microbe population balanced. In the hindgut, microbes work to ferment your horse’s feeds and forage. The beneficial bacteria break down fibrous plant material, producing volatile fatty acids as by-products. These volatile fatty acids can lower the pH of the hindgut, making it more acidic. You may have heard about hindgut acidosis – this is what’s going on. 


  • Hindgut buffering agents like bicarbonate and phosphate help counteract this acidity by neutralizing the volatile fatty acids, thus helping to maintain a stable pH. Hindgut buffers are helpful to keep the digestive system steady, which may help reduce the excessive water in your horse’s manure.


lush pasture in fall

More grazing, more walking, more outside time, more herd time. 


Change the management of horses:


  • This can involve increasing your horse’s exercise routine, providing more turnout time, and reducing stress to help improve overall digestive health.


  • For horses living in a herd, consider reducing the herd size or making some strategic shifts of horse buddies if your horse is at the lower end of the social hierarchy. 


  • If possible, feed supplements and feeds separately to reduce the stress of competing for food. If you supplement your turnout areas with hay, create more feeding stations than there are horses.  


Get your vet’s help


  • Your vet can help with your horse’s diet and prescribe meds and supplements to support healthy digestion. Your vet can also do a fecal egg count and give your horse the appropriate deworming medication to reduce the impact of internal parasites.


  • Digestive enzymes, such as amylase and lipase, may be added to your horse’s diet to help break down and better utilize the nutrients in their food.


  • Your vet should also help rule out gastric ulcers and other foregut issues, and keep tabs on your horse’s body weight and body score.  


vet listening to a horse's heart

You vet is pivotal to unraveling so many horse mysteries.


What is a fecal transplant in horses?


  • Your vet can also help with a fecal transplant in horses, also known as a fecal microbiota transplant (FMT). This procedure involves fecal matter from a healthy donor horse transferring into the gastrointestinal tract of a horse with digestive problems. It’s like donating probiotics from horse to horse. But fancier probiotics. And more expensive probiotics.  


  • And before you get any ideas about cooking up some manure treats in your air fryer, know that the procedure involves collecting fecal matter from a healthy donor horse and processing it in a lab. Then, the donation is delivered via an enema or nasogastric tube. Essentially, your vet will dose it with a tube at either end. Fecal transplants treat watery feces because they help stabilize the gut microbiota, improve digestion, and reduce diarrhea in horses.


Grooming the horse with free fecal water syndrome


Grooming the FFW mess is a time investment. You will need to spend extra time cleaning up and messes, then do some things to help prevent more. 


How do you groom the messy tail?


  • In warm weather, start with a shampoo. Use something mild, and you may want a heavily scented shampoo to deal with any odors.  


  • Then, it’s time to condition the snot out of the tail. Use a grooming oil, and don’t be shy about it. Let that grooming oil sit for 5 or 10 minutes; then, you can slowly start picking out the tangles from the bottom up. Use your fingers or a wide-tooth comb. This can take a hot minute.  


  • If your horse’s tail is super oily now, use that mild shampoo again to remove some of the oil. Leaving some in is helpful, hoping fecal water will “slide” off the tail. 


  • You may have to skip the shampoo in the colder months, but you can still use a no-rinse shampoo and many hot clothes to clean the tail. Then add your horse grooming oil and get to picking out those knots. 


washing a white tail

Get used to using blueing shampoos!


How to prevent more tail mess


  • Make your horse’s tail as conditioned as possible. Use oils, conditioners, or whatever you have to keep the hair soft.  


  • Braid the tail. You could create a loose braid below the tailbone. Experiment with adding a tail bag – sometimes, this helps keep the hair out of the way, and sometimes, the tail bag acts like a giant sponge that soaks up any free water and glues it to the tail. 


  • Or, you can create a loose braid at the top of the tail. Many horses have shorter hairs directly off the tailbone. A loose French braid keeps them out of the way.  


  • If your horse wears blankets, replace any tail cords with leg straps (or vice versa). Tail cords often become a urine and manure distribution system. Elastic straps around the hind limbs tend to be less of a target and may help your horse’s legs stay cleaner.  


  • Also, consider removing the tail cover from your horse blankets. This will hopefully allow your horse to lift their tail higher and keep that free fecal water away from the hair.



Vaseline and grooming oil protect the hind legs.  Grooming oil is also great for the tail.


How do you groom and protect the stained legs?


  • This is where you need to be careful. Obviously, we want to clean the legs but not irritate them further. Use a warm water rinse to remove as much as possible. Think of this as warm-water hosing; you may be there for a while. Add in the gentlest shampoos you have – no detergents, no Orvus, no dish soap. Your horse needs all of the sebum his skin can make to protect that area, and detergents and dish soap will strip it right off.  


  • Let the legs dry, and cross your fingers that they don’t get any drips.  


  • Now, it’s time to protect the skin. The easiest and messiest way is to smear a barrier cream like zinc oxide or petroleum jelly on affected areas. But this can also make shavings and dust stick, so make sure your horse’s bedding is wickedly clean and you smear off any accumulated dirt before you reapply any ointment.  


loose braid to avoid urine

Braid the upper part of the tail – loosely – to keep the hair out of the water stream. 


Like all things horses, it’s part detective work, giant mess cleanup, preventative care, and experimentation. 



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Thank you! 





Some citations if you like that kind of stuff! 


Stewart, A. J. (n.d.). Free fecal water syndrome in horses. Merck Veterinary Manual.


Laustsen L, Edwards JE, Hermes GDA, Lúthersson N, van Doorn DA, Okrathok S, Kujawa TJ, Smidt H. Free Faecal Water: Analysis of Horse Faecal Microbiota and the Impact of Faecal Microbial Transplantation on Symptom Severity. Animals (Basel). 2021 Sep 23;11(10):2776. doi: 10.3390/ani11102776. PMID: 34679798; PMCID: PMC8533009.


Citation: Murray, M.J., Grovum, W.L., Al Jassim, R.A.M. (1996). “Effect of pH on microbial fermentation and activities in the caecum of the horse.” Journal of Applied Science, 81(7), 1381-1384.

Loving, P. by N. S. (2023, December 21). Free fecal water syndrome explained. The Horse.