Sand colic is a term that refers to abdominal pain due to irritation or impaction of the gastrointestinal tract after the horse ingests sand. In some instances, accumulation of sand can create complete blockage of the tract.

When grazing sandy pastures or eating hay off the ground, horses often pick up bits of sand. In sandy soils, grass may be pulled up and the horse may ingest sand clinging to the roots. A horse may eat a little sand as he cleans up the last wisps of hay that gets pulled out of a feed rack or kernels of grain spilled from a tub.

Even in regions that don't have sandy soils, many horse owners have a sacrifice area where they keep horses confined when pastures are wet or overgrazed, or a round pen, or a place they can confine an injured horse.

To keep the pen from becoming too muddy, they often dump a load of crushed stone/sand/gravel in the confinement pen or riding ring. Fed on that surface, horses may ingest sand.

Ingested sand usually moves through the digestive tract with food and passes out with manure, but it can irritate the intestinal lining along the way. If a lot of sand accumulates, it weights down the gut and may impair motility, hindering proper digestion and function. Irritation of the intestinal lining can lead to diarrhea, weight loss and colic.

If sand collects in the tract, reduction in motility hinders passage of the sand and leads to more accumulation. With a blockage, the horse will need surgery to remove the sand.

Horses that live in sandy areas ingest various quantities of sand. Why it becomes a clinical problem in some horses - and others carry fairly heavy sand burdens without having a problem - is not understood. Some horses deliberately eat sand, possibly from curiosity or boredom. Some eat grass down to the roots and eat sand with the roots.

When sand becomes a problem, it's usually in the colon. Sand moves through the rest of the tract fairly quickly. But when it gets to the large colon it tends to settle. This is probably due to motility patterns of the large colon; the sand may be retained in some parts while everything else is moved on through.

When a horse becomes impacted, medical treatment is tried first, to move the sand on through. If that doesn't work, the sand must be surgically removed.

Medical treatment usually consists of treating the horse with a combination of psyllium and mineral oil via nasogastric tube. This can be done repeatedly until the blockage is relieved. The combination of mineral oil and psyllium helps lubricate the intestinal contents and get things moving.

The fibrous psyllium tends to swell (absorbing moisture from the digestive tract) and pick up sand and carry it along, moving it out of the tract with the manure.

If you think your horse may be eating sand, you can do a fecal sand test to watch for sand in the manure, and then use a sand-clearing type of supplement periodically if you find sand. There are several psyllium products for horses. Or, you can buy huge economy size human psyllium products, which work just as well - if your horse will eat the psyllium with their feed.

Don't feed it every day for a prolonged period of time; after a couple weeks, the horse's gut bacteria adapt to this added fiber and start to break it down. If you feed it continually, it doesn't work as well anymore for clearing the sand out.

It's best to feed it intermittently (such as for one week per month or one week every few months, depending on the level of your problem) if you are trying to prevent sand colic. Read and follow label directions on equine psyllium products.

The most important thing is prevention. If horses are fed on the ground, put the hay in a place where the horse can't consume sand, or put down a rubber stall mat to feed on - something to keep the horse from eating sand. Avoid overgrazing a pasture, especially on sandy soils. Grazing the plants down to the roots will generally result in ingesting some sand.

A study published in the February 2008 issue of the Journal of Equine Veterinary Science looked at using probiotics and prebiotics in conjunction with psyllium. Sand produces irritation and may lead to decreased gut motility which in turn may lead to impaction.

As the tract slows, digestion suffers, the microbe population in the hindgut is altered, which in turn has a negative effect on digestion and motility. It's a vicious cycle.

So the researchers added probiotics - some of the normal, helpful microbes that must be present at proper levels in the hindgut for optimum digestion and breakdown of fibrous material. The idea was that adding these microbes might help keep gut motility at a more normal rate, which might help move sand on through.

Due to this research, some new products were created, combining psyllium and probiotics in pelleted form to be added to feed.

CHECKING FOR SAND - You can test your horse's manure for sand by filling a 2 to 4 quart plastic container about 2/3 full of water and adding about 6 fecal balls. After stirring it, sand will settle. Pour off the water slurry and any sand will remain in the bottom of the container.

One negative test (no sand) does not prove that there's no sand in that horse's gut; you must check several samples, over time.

You can also check a manure sample by putting a fecal ball in a plastic rectal sleeve (that your veterinarian would use for rectal palpation) with some water and do a swirl test. Pick up the fecal sample with a plastic rectal sleeve/glove, then turn the sleeve inside out so it contains the sample, pour water into the sleeve and mix the water with the feces by shaking it.

When you let everything settle, the sand (being heavier than manure) will gravitate down into the fingertips of the sleeve/glove.

These tests simply tell you the horse has eaten sand and it made its way through the tract with the manure. It doesn't tell you how much sand the horse still has inside, or whether he will colic or develop impaction.

A fecal test is a rough indicator, however, because if there is consistently a lot of sand in the feces there is probably a lot of sand in the colon, but the test may be negative in horses that are passing small amounts of sand.

Your veterinarian can listen to the ventral abdomen with a stethoscope, and hear the sand moving. The rustling sounds like the sea moving off a sandy beach. Whether or not sand can be heard might depend on where the sand is in the tract, and the amount. Sand will also show up on radiographs because it is so dense.