When grazing on sandy pastures or eating their feed off the ground, horses often pick up bits of sand or silt. Even if the horse is fed in a bucket, tub, or feed rack, he might still eat spilled feed from the ground and ingest a little sand. Horses pastured in regions with sandy soils might eat small amounts of sand clinging to grass roots when grazing.
Sand moves through the digestive tract with food and passes in manure, but some sand can accumulate within the tract. These residues can weigh down the intestine, impair motility, and cause impaction. Sand scraping the intestinal lining can lead to irritation, diarrhea, weight loss, and colic in some horses.
David Freeman, MVB, MRCVS, PhD, Dipl. ACVS, Appleton Endowed Professor in the University of Florida’s Department of Large Animal Clinical Sciences, in Gainesville, says sand impaction is a relatively common cause of colic in sandy regions when it accumulates in the gastrointestinal tract. “Some horses deliberately eat sand, possibly out of curiosity or boredom,” he says. When sand accumulation causes a problem, it is usually in the last segment of the large colon, where it tends to settle out.
Diagnosis
One way to know if a horse is passing sand in his manure is to pick up a fecal sample with a plastic bag or rectal sleeve, then turn it inside out so it contains the sample. Pour in some water, shake it up, and then let everything settle.
“The sand, being heavier than the manure, will sink into the fingers of the sleeve or bottom of the bag,” Freeman says. “Finding sand in the sample merely tells you that the horse has eaten sand that has made its way through the gastrointestinal tract. It doesn’t tell you how much sand is still in the tract or whether the horse will colic. This test can be a rough indicator; however, if there is sand in the feces, there is probably sand in the colon.”
Have your veterinarian check the horse and listen to the ventral (forward) part of the abdomen with a stethoscope. He or she might hear the sand moving, amid the sound of intestinal movements. Sand is also visible on radiographs. “On radiograph we can usually see the outline of an accumulation of sand in the large colon in the ventral part of the abdomen,” says Freeman.
Radiographs can help veterinarians understand roughly how much sand is in the large colon. Ultrasound examination can often help in colic diagnosis but is not as helpful for sand impaction because on ultrasound, sand can look similar to gas in the large colon, he adds.
Treatment
“When dealing with horses that have eaten sand, we usually try to move the sand through (the digestive tract),” says Freeman.
Some owners might feed psyllium as both a preventive method and a treatment. This is a high-fiber product that might stimulate gut motility, help collect sand particles, and make it easier for the horse to pass the sand through the tract intermingled with the psyllium. Horses naturally eat a lot of fiber, however, so the addition of psyllium might not increase the total fiber content much.
Another drawback is psyllium (just like other fibrous feeds) might be broken down by bacteria in the hindgut, reducing the amount available to carry sand through. Psyllium might work in some horses and not others. Other treatments to move the sand include mineral oil, magnesium sulfate, and other laxatives, but these typically work best if combined with psyllium.
Psyllium pellets are available to add to horses’ feed, but owners must ensure horses do not consume more than the recommended dose. “Psyllium itself can form impactions if given in excess,” Freeman says.
“Surgery to remove sand blockage is usually successful,” he adds. “The large impactions can be more difficult to remove surgically because the intestine is very heavy when filled with sand, but these horses respond quite well.”
After having the sand removed, the horse should not go back into a sandy paddock, if possible, says Freeman. A combination of probiotics and prebiotics in conjunction with psyllium might improve gut motility to keep sand moving through. If the tract slows, digestion suffers, and alterations in the hindgut’s microbe population can have a negative effect on digestion and motility.
