Fixed the Fecal Water but Something Still Feels Off? What Hindgut Health in Horses Really Depends On
If you have managed fecal water, you know the morning routine: bucket, sponge, tail tied up, hind legs scrubbed before anything else gets done.
The owner of a 25-year-old half Arabian had tried, in her words, everything before something finally worked. "Pretty much the only time I'm not cleaning his bum on a daily basis is when he is on your product," she wrote. Her next question was whether she could keep feeding it every day.
It is a fair question about hindgut health in horses, and it points to a bigger one: why does a problem you already solved keep finding its way back?
Part of the answer is in how horses were built to eat. The equine hindgut evolved around grass eaten slowly, almost all day, by an animal walking across living pasture. Modern horsekeeping changed nearly every piece of that: meals instead of grazing, stored forage instead of growing grass, small paddocks instead of open ground. The hindgut copes with a great deal, but it was never designed for constant change, and modern routines are full of it. A steadier gut usually comes from putting some of that old consistency back.
Our guide to fecal water syndrome covers getting the water under control. This piece is about what comes after.
Why Does Fecal Water Come Back?
Researchers still do not fully understand fecal water syndrome, which is worth knowing before you blame yourself for a relapse. In a German field study, many owners of affected horses described them as low in the herd's pecking order, and about a third saw symptoms only in winter. A 2021 Scandinavian study that paired 50 affected horses with 50 unaffected horses on the same farms found the affected horses ate roughly twice the concentrate and less straw, while turnout and feeding routines looked about the same. Some owners saw the water ease after switching to a different forage harvest, to hay, or to pasture.
In practice, fecal water rarely has one cause with one cure. It tends to show up when several pressures stack together: a starchier ration, a new batch of forage, a lower spot in the herd, the turn into winter. Remove one and the water may clear. Add another later and it can return, even though nothing you fixed has come undone. If you are not sure how much starch the rest of the bucket adds, run your horse's ration through our Diet & NSC Calculator.
Hindgut Health in Horses Depends on Steadiness
The hindgut, meaning the cecum and colon, is where your horse's microbes ferment fiber into energy, and those microbes respond to almost everything. A 2020 research review lists diet and supplements, exercise, antibiotics and dewormers, age, transport and weaning among the factors that shift them.
Every change in your horse's week reaches the hindgut eventually. A new hay supplier, a trailer ride, a course of medication, a new pasture buddy: the microbes adjust to each one, and a sensitive horse feels the adjustment. One owner said her PPID Haflinger is so suspicious of anything new that she "will go off food for weeks at a time if things are different." Not every horse is that dramatic. Most are more sensitive than they let on.
So the most reliable hindgut support is deliberately boring. Keep the same forage source as long as you can get it, and make changes over a week or two. Keep forage in front of the horse most of the day. For a horse at a healthy weight, that means at least 1.5 percent of body weight in forage dry matter daily, which works out to about 18 pounds of hay for an 1,100-pound horse, since hay is roughly 90 percent dry matter. And keep the bucket simple enough that you can tell what actually helped.
The Piece Nobody Mentioned When You Fixed the Water: Sand
Horses swallow some sand and soil just by eating, especially when hay goes out on the ground or grass is grazed short. Our piece on why horses can have sand in the gut even off sandy ground covers where it comes from. What stands out is how common it is. In a Swedish study, 20 of 30 horses admitted to a university hospital for reasons unrelated to colic, 66 percent, had at least one sand accumulation on radiographs. They lived in an area where sand impaction was considered uncommon.
Small amounts often cause no trouble. Larger accumulations are linked with chronic intermittent diarrhea, weight loss, poor performance and colic that keeps returning. Intermittent is the important word. A hindgut irritated by sediment does not act up every day, so it is easy to blame the hay, the weather or the horse's mood. Sand does not explain every case of loose manure, but manure that keeps going loose after you thought it was handled is a good reason to rule it in or out.
How Do You Know If Your Horse Has Sand?
Most people start with the bucket test, and it is worth doing properly. Take two fecal balls off the top of a fresh pile, so you are not picking up soil from the ground. Drop them into a clear plastic sleeve or a heavy plastic bag about half full of water, break them up and mix thoroughly, then hang it tilted so anything heavy settles into one corner or the fingertips. Give it time to settle before you look and feel along the bottom. A few grains are not a concern. A visible layer suggests a fairly large sand load and is worth a call to your vet.
A clean result does not clear your horse, though. In one comparison, the glove method turned up sand in fewer than half the manure samples from horses whose sand was confirmed by other methods. A horse carrying a real accumulation may not pass sand in that day's manure, so a few samples taken on different days tell you more than one.
Your vet has better tools. Radiographs are the most reliable way to see and measure sand, though they usually mean a hospital visit. Ultrasound can be done on the farm but is more subjective. Keep it in proportion, too. The Swedish researchers cautioned that small accumulations are common enough that they should not be named as the cause of gut trouble until other possibilities are ruled out. Ulcers, teeth, parasites and forage quality can all look similar from the outside, which is why this conversation belongs with your vet.
How Do You Help Prevent Sand Buildup?
Management comes first, and no product replaces it. Feed hay in feeders, nets or on mats instead of bare ground, keep forage available most of the day, and keep clean water in front of your horse. A horse eating plenty of fiber and drinking well moves sediment along far better than one nosing the dirt for every last stem.
For horses with ongoing exposure, a periodic purge can help, and if you have been asking where the research is, thank you. It is the right question. Psyllium, the familiar option, has a mixed record. A 1998 study in ponies found it did not speed sand removal, while a Finnish study found psyllium plus magnesium sulfate, given by a vet through a stomach tube, cleared sand effectively. One owner of a 23-year-old rescue gelding had fed psyllium daily for more than two years and still fought sand every month, even though, as she put it, "I feed in feeders and do all the preventative I can."
Sand-Less takes a different route. It is psyllium free and made from four whole ingredients: cold-milled golden flax, chia seeds, tapioca pearls and fennel. When flax and chia meet water, they form mucilage, a soft gel designed to spread through the gut contents and help carry fine sediment with it. You activate it with a splash of water and feed it once a day for seven days, repeating monthly or as needed: one cup for a pony under 800 pounds, two cups for a horse under 1,350, and three for horses over 1,400. It contains no molasses, sweeteners, grain, soy or corn, has also been third-party tested by Equi-Analytical, with ESC plus starch measuring 18.0% as sampled, and a fennel-free version is available for pregnant mares.
As for the evidence, Sand-Less has not been through a published clinical trial. Before it went on sale, we followed it for more than a year in several barns of 20 or more horses, alongside each barn's own veterinarians, and the vets reported that horses with existing sand accumulations were clear within a couple of months. The rescue gelding's owner put it more simply soon after starting: "for the first time I have a clean fecal!" If sand showed up on your own horse's test, ask your vet about rechecking after a couple of monthly purges, so you are measuring the result instead of guessing.
A Steadier Gut Takes More Than One Fix
If the water is back right now, start with our fecal water syndrome guide and get your horse comfortable again. Then look past the symptom. What changed in the weeks before it returned? A new hay load, a colder month, a new horse in the field, a trailer trip? Is hay still going out on the ground? Has anyone checked for sand in the past year?
As for that first owner's question, Sand-Less is built as a seven-day purge, not a daily feed. The daily work happens elsewhere: steady forage, slow changes, and knowing whether sand is part of your horse's picture. None of it is dramatic. A gut that gets that kind of attention gives you fewer surprises, and when it does act up, you will have a much better idea why.
Next read: For the everyday signs that the gut is out of balance, 5 Signs of Poor Gut Health in Horses picks up from here.
References
Kienzle, E., et al., "Field Study on Risk Factors for Free Fecal Water in Pleasure Horses," Journal of Equine Veterinary Science, 44, 32–36, 2016 (social rank, winter-only symptoms)
Lindroth, K.M., Lindberg, J.-E., Johansen, A., and Müller, C.E., "Feeding and Management of Horses with and without Free Faecal Liquid: A Case–Control Study," Animals, 11(9), 2552, 2021 (50 paired cases and controls, concentrate and straw differences, similar management, forage changes that helped)
Garber, A., Hastie, P., and Murray, J.-A., "Factors Influencing Equine Gut Microbiota: Current Knowledge," Journal of Equine Veterinary Science, 88, 102943, 2020
Karasu, G.K., with Barakat, C., "Is Your Horse Getting Enough Hay?," EQUUS, October 2021, updated October 2025 (minimum 1.5 percent of body weight in dry matter for horses at a healthy weight)
Kendall, A., Ley, C., Egenvall, A., and Bröjer, J., "Radiographic Parameters for Diagnosing Sand Colic in Horses," Acta Veterinaria Scandinavica, 50:17, 2008 (20 of 30 control horses with sand, low-sensitivity sedimentation test, caution against assuming sand is the cause)
Thal, D., "Checking Manure for Sand," Horse Side Vet Guide (sample collection, sleeve or bag method, interpreting a few grains vs. a layer)
Kentucky Equine Research, "Diagnosing and Treating Sand Colic in Horses" (glove method found sand in fewer than half of confirmed cases)
Kaikkonen, R., Niinistö, K., Lindholm, T., and Raekallio, M., "Comparison of Psyllium Feeding at Home and Nasogastric Intubation of Psyllium and Magnesium Sulfate in the Hospital as a Treatment for Naturally Occurring Colonic Sand (Geosediment) Accumulations in Horses: A Retrospective Study," Acta Veterinaria Scandinavica, 58:73, 2016 (signs linked to sand, radiography as most reliable detection)
Kilcoyne, I., "Sand Colic in Horses: Diagnosis, Treatment, and Prevention," TheHorse.com, June 2024 (fecal tests not always accurate, sand may be absent from manure, radiographs vs. ultrasound, feeding off the ground)
Hammock, P.D., et al., "Failure of Psyllium Mucilloid to Hasten Evacuation of Sand from the Equine Large Intestine," Veterinary Surgery, 1998
Niinistö, K., et al., "Comparison of the Effects of Enteral Psyllium, Magnesium Sulphate and Their Combination for Removal of Sand from the Large Colon of Horses," The Veterinary Journal, 2014
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