Rarely do we see our horses lapping up sand like it's some rare commodity. But inevitably horses end up with burdens of sand in their intestinal tracts from grazing sandy pastures or eating off the ground. In areas with sandy soil, horses might pull up grass and ingest sand clinging to roots. Horses fed on the ground might eat sand as they clean up the last wisps of hay or kernels of grain. Even if fed in buckets or feed racks, horses might eat spilled feed from the ground. Intestines can be obstructed with sand, causing colic.
Sand moves through the digestive tract with food and is passed in manure, but it can irritate the intestinal lining along the way. This irritation can lead to diarrhea, weight loss, and colic. If sand accumulates, it weighs down the intestine and can impair motility, hindering proper digestion and function. Reduction in motility hinders passage of sand and leads to more accumulation, and in some cases the slowdown and accumulation cause a blockage.
David Freeman, MVB, MRCVS, PhD, professor and interim chair of the Department of Large Animal Clinical Sciences and chief of staff of the Alec P. and Louise H. Courtelis Equine Hospital at the University of Florida, says sand impaction is a well-recognized cause of colic. "Why it becomes a clinical problem in some horses-- while others seem to carry fairly heavy sand burdens without a problem--is still not understood," he says.
"When sand becomes a problem, it is usually in the colon," he explains. "Sand moves through the rest of the tract fairly quickly. But when it gets to the large colon it tends to settle out, probably due to motility patterns of the large colon."
"One method to see if a horse is passing sand is to collect some of the horse's manure and do a swirl test," says Freeman. "Pick up a fecal sample with a plastic rectal sleeve, turn it inside out so it contains the sample, pour water into the sleeve, and mix the water with the feces. After you shake it and let everything settle, the sand (being heavier than manure) will gravitate down into the fingers of the glove.
"That's one way to check for sand, but all it tells you is that the horse has eaten sand and that it has made its way through the gastrointestinal (GI) tract," he says. "It doesn't tell you how much sand the horse still has in the tract or whether he will colic. But if there is consistently sand in the feces, there is probably sand in the colon."
There are other ways to make a diagnosis. The veterinarian might listen to the abdomen with a stethoscope. "You can hear the sand moving; it sounds like the sea moving off a sandy beach," he describes. "Whether or not you hear this rustling, however, might depend on where the sand is in the tract, and the amount of sand."
Sand will show up on radiographs because it is very dense. Not all horses with sand in the tract show signs of colic. Some have diarrhea and lose weight, but this is rare. "These horses are a diagnostic challenge because those signs can be caused by different things," says Freeman. "You will be treating them medically, so it is important to have an accurate diagnosis. In these cases we think sand damages the intestinal lining, since it is rough and irritating. Radiographs are useful if you suspect sand because you might be able to see the outline of an accumulation in the large colon, and it can give an impression of how much sand is there."
Ultrasound examinations aren't as helpful as radiographs, but they can be used.
Melinda Freckleton, DVM, of Haymarkert Veterinary Service in Virginia, says she rarely radiographs horses for sand accumulation because her practice is a field service, and special radiographic equipment is needed to image the abdomen.
While some veterinarians first try to treat horses with accumulated sand medically, some horses require surgery if these efforts to move sand aren't successful. Freeman says, "We then have to put the horse under anesthesia and physically remove the sand from the colon."
In situations where you can't prevent sand ingestion, feeding the horse fibrous products such as psyllium might help. Psyllium tends to swell, pick up sand, and carry it along, moving it out of the tract with manure. There are numerous psyllium products available for horses.
"Psyllium is a laxative, something we borrowed from human medicine," says Freeman. "It is a high-fiber product that may collect sand and make it easier for the horse to pass it on through the tract, and it may stimulate motility. But horses eat a lot of fiber to begin with. Addition of psyllium may not increase the total (GI) fiber content a lot. The other problem with using psyllium in the horse is that it might be broken down by bacteria in the hindgut (large intestine and cecum)," leaving less to carry sand on through.
Psyllium might work in some horses and not in others, and horse owners should not rely on it alone. If they don't make other management adjustments to reduce sand ingestion, the horse can still become overloaded with sand. "There are many products available for horses," says Freckleton. "Or, you can get giant economy-size human psyllium products at a discount store. But don't feed it every day for more than a week or two because the horse's gut will adapt to the added fiber and start to break it down. If you feed it continuously, it won't be clearing out sand anymore. It's best to feed on an intermittent basis such as one week per month."
Additional treatments for sand impaction include mineral oil, magnesium sulfate, and other laxatives. "At this point we're still not sure what works best," says Freeman. "It may vary from horse to horse. Most of the treatments we use are quite safe and not very expensive."
Surgery, if needed, is usually successful--sand impaction is not a death sentence. Freeman says the surgery is uncomplicated, although horses with larger amounts of sand can be more difficult because the sand makes the intestines heavy.
"Some surgeons put psyllium inside the colon itself before closing it up to remove any more sand that might be in there," says Freeman. "It is impossible to remove it all; you always leave some behind."
Freeman's main interest is colic surgery, and he's spent much of his career in Illinois and Florida--areas with plentiful sand. "I saw a lot of sand colic in Illinois in horses treated with psyllium," he says. "After we removed sand by surgery, we advised owners that the horses should not go back into sandy pastures or pens, but this was not always possible, so we recommended they continue with psyllium. Then these horses would come back later with another impaction, even though they were on psyllium. Our concern was that it wasn't completely cleaning out the sand, so we did a research project looking at psyllium.
"We put sand into the cecum of ponies because this was an easy place for surgical access," Freeman says. "It doesn't stay in the cecum; it immediately moves into the large colon. This was an easy way to create a model of sand accumulation in a normal colon."
After he and his colleagues performed surgery to place the sand, they treated the ponies with psyllium. The ponies were to be euthanized at a certain stage for other reasons. "We knew how much we put in and were able to see, after 11 days, how much remained" in the large colon, he says. "There was no difference between the ponies treated with psyllium and the ones that were not. Both groups had the same amount of sand in the large colon."
Freeman notes that psyllium treatment is controversial: "A lot of people don't accept the results of our study, probably because psyllium is usually used in feed for horses continuously eating sand."
The argument is that if you feed psyllium to a horse that is continuously eating sand, it might carry enough of the sand through that it won't accumulate to problematic levels. But Freeman's study assessed the recommended dose of psyllium as a means of treating an established sand impaction.
Finnish researchers studied sand accumulation via radiographs in horses that had a naturally developed sand burden. "They found that radiography was a good way to monitor the resolution of sand impaction, but they didn't always get a consistent response with psyllium," says Freeman. "It worked in some horses, but not in others. When it didn't work, they had to treat those horses with something else--usually mineral oil."
The oil helps lubricate contents of the tract and gets things moving. Some of the horses received magnesium sulfate (Epsom salts) or another laxative.
Freckleton explains that when she treats a sand impaction medically, she uses a combination of psyllium and mineral oil via nasogastric tube, repeating until the blockage is relieved.
Scientists in Austria completed a study using this combination in two groups of horses that were fed sand. One group was treated with mineral oil only, and the other received mineral oil in combination with psyllium. The group that received the combination of oil and psyllium did best, but there was a lot of variability.
Freeman suggests this variability could be due to a variety of physiologic reasons, one being differences in GI tract motility between animals.
Preventing Sand Accumulation
There are ways you can attempt to cut back on the amount of sand your horses ingest. Freckleton says even though soil is not sandy in Northern Virginia where she practices, she still sees cases of sand colic, often when owners are feeding in a dry lot and managing their pastures responsibly.
"They are being good stewards of their pasture and make a sacrifice area where they can keep horses off pasture when it's wet or overgrazed," she explains. "To keep the pen from becoming muddy, they often dump a load of crushed gravel in the confinement area. Also, if a horse needs temporary confinement for some reason, it might be kept in a round pen or riding ring, where footing might be crushed gravel or sand.
"When I do routine work at places where I know they're keeping the horse in a sandy lot, I encourage owners to feed on a mat and learn how to do a fecal sand test and use a sand-clearing supplement if they find sand in manure," she adds.
Horses that are kept in dry lots or graze in sandy areas are susceptible to eating sand. There are management measures you can use, including hay racks, mats, and feeders, to help prevent sand ingestion with food. You also can help your horse pass sand through his digestive tract and stop accumulation, possibly avoiding surgery.
About the Author
Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog, www.heathersmiththomas.blogspot.com, she writes a biweekly blog at http://insidestorey.blogspot.com that comes out on Tuesdays.
POLL: Laminitis Experience