Tuesdays with Tony

Hey, kits! This week I’m going to fulfill a reader request (yes, I can read) and frequent topic of quandary around here: fecal water syndrome. Before you accuse me of coming up with fancy names for diarrhea, let me assure you, fecal water syndrome is different. These horses have normal, formed manure, along with poop-colored water, and both are expelled at the same time. That lovely brown watery substance then sticks to the tail and hindlimbs to create as much work as possible for you, the human caretaker. So without further adieu, let’s talk watery poop!

What is it??

“Differential defecation of solid and liquid phases” is how it was described in a research paper from 2020. Seems an appropriate description! That’s exactly what these horses do; they poop normal solid apples, along with brown colored water. Very different from diarrhea. Some horses also show some signs of painful defecation as well. This is often demonstrated by picking up and replacing alternating hind limbs. You humans would probably call it ‘the peepee dance’ in a 4-year-old child. However, many horses show no signs of pain, in general, or discomfort of any sort. These horses are similar only in the fact that they both have excess fecal water.

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Who gets it?

The study mentioned above found the syndrome in all colors, breeds, ages, and sexes of horses. Older geldings with bad teeth were slightly overrepresented. However, in most horse studies where age is a factor, older geldings are also overrepresented (small rabbit hole here!). It is generally thought that this occurs because geldings are more likely to be well loved older horses due to their good behavior (like me!).

I feel this should be a warning to all chestnut mares out there. It also likely reflects that mares and stallions may be used for breeding, and this is generally linked to increased health problems at younger ages. This study was looking at haylage consumption in particular, but in the process found that horses of all kinds of different sorts of feeding regimes were susceptible to fecal water syndrome. 

So what’s going on in there?

Great question! Most smart humans agree, they don’t know (which is why they asked The Cat). There’s almost certainly some disruption of the normal bacteria, viruses, and fungi in the GI tract. Yep, that’s right – the normal GI tract has all those icky-sounding things. But why this disruption happens is the $64,000 question. Current best thoughts among smart humans like my Docs are:

  1. A GI tract that can’t handle long stem forage (probably a significant factor in the senior horse that’s got bad teeth)
  2. A GI tract that doesn’t like grain
  3. An inflammatory response in the GI tract (think allergies here)
  4. A general revolt by the good bugs in the gut with a takeover by the bad guys

So you can see it’s a complex question with a lot of potential answers. One thing I did find interesting in my research for this week’s blog, is that horses with fecal water syndrome also have a higher reported incidence of colic than normal horses. 


Surely, I jest. If no one knows why this happens, how can even smart humans like my Docs treat them? Well, treatment is aimed at making the GI tract happy. But how??? Let’s start with basic guidelines. With any treatment, time is needed. This means patience, which is not something you humans do well. It’s not easy, but it usually starts with diet changes, and having patience.

My Docs start by evaluating the diet and then, depending on their findings, either increasing hay, or getting rid of it altogether. I realize this sounds drastic, but poopy water causing stinky, icky tails and hind legs calls for drastic measures! This diet change will be tried for at least 3 weeks. Along with diet changes, a good probiotic that contains Saccharomyces boulardii is added in. If no improvement occurs, then the next step is usually anti-inflammatories in the form of low doses of steroids like dexamethasone. These work by telling the gut immune system to calm down, stop being so dramatic, and let everything settle. A typical course of treatment would start with a higher dose, then taper down. 

Finally, if diet changes and anti-inflammatories don’t work, my Docs pull out an antibiotic called metronidazole. This antibiotic is used to kill a group of bacteria called anaerobes. The most common bad guys in the GI tract (human and horse) are anaerobes. Metronidazole has a slightly different use here than the wholesale destruction of bacteria antibiotics usually perform. Here, metronidazole is used to decrease the numbers of anaerobes and try to set up a better environment for the happy bugs. This means lower doses, or tapering doses may be used which is way, way different than the way antibiotics are normally prescribed. 

Sometimes one or more of these combined treatments helps, sometimes not. If these treatments fail, my Docs generally recommend allergy testing or limited source diets to see if an allergic cause can be narrowed down. They may also bring in an equine nutritionist to evaluate all kinds of things like fiber and starch content of the diet, and to help formulate a balanced diet if limited ingredients are going to be tried. My Docs may also try something called fecal transfaunation. This involves taking the manure of a normal healthy horse, mixing it with water, and giving it via NG tube to a horse with fecal water syndrome. Like all treatments for fecal water syndrome, sometimes it works, sometimes it doesn’t.

Besides the endless tail and leg washing, fecal water syndrome is a giant pain in the behind (literally!!!). With a lot of patience and some experimenting with feed sources, good probiotics, and maybe some pharmaceuticals, my Docs can work with you to get your horse back to normal. Now, be a good human and scroll down a bit and subscribe to my blog, if you haven’t already!

Until next week,



P.S. If you want to take a really deep dive into fecal water syndrome, my docs did a podcast on this very topic! Just hop over to the Podcast Page and scroll down through the list until you see it. I’m sure you’ll see 

Tuesdays with Tony is the official blog of Tony the Clinic Cat at Springhill Equine Veterinary Clinic in Newberry, Florida. If you liked this blog, please subscribe below, and share it with your friends on social media! For more information, please call us at (352) 472-1620, visit our website at SpringhillEquine.com, or follow us on Facebook!

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