Impaction Good management can reduce the chances that this equine killer will strike your horse. Impaction in horses sometimes goes unnoticed in its early stages because the first signs are usually mild. Yet, if the condition is not treated and corrected, impaction can be just as serious and as potentially fatal as a more acute type of colic. Some types of impaction are also difficult to treat, such as impaction of the cecum, which completely blocks the opening into the rest of the large intestine.
The horse is susceptible to many types of colic. He has a small stomach, chews his food only once, and the food leaves the stomach in rather rough, undigested form. It is not processed by microorganisms and further broken down and digested until it reaches the cecum (the large pouch connecting the small intestine with the large one).
Problems can occur in several places along the tract because it is so long and irregular. Rough masses of food can lodge in a narrow spot such as the valve between the small intestine and cecum, or at the opening from the cecum into the large intestine. The horse is prone to colic because of the great activity of the small intestine and the large amount of undigested food that moves on into the large intestine. Cows have fewer problems, with their large fermentation compartments at the beginning of the tract, putting forth only fine and well-digested material to be conveyed through the intestines.
Impaction can occur in horses because of the type of food eaten, the manner in which it is eaten (such as a hungry horse bolting his food without chewing properly), or because a horse with poor teeth is unable to chew roughage well enough. Horses have been known to impact the cecum by eating lawn clippingsgobbling down too much of the fine, palatable grass in a hurry without chewing much. The most common culprit, however, is coarse feed, poor quality roughage, or over-mature hay or straw (as when a horse eats his bedding).
Even if coarse roughage is well-chewed or -chopped, it may cause trouble if it passes through the stomach undigested and collects at the end of the small intestine by the valve into the cecum, causing complete obstruction. If blockage at this valve occurs, the horse may be mildly uncomfortable at first, perhaps pawing or looking around at his flank, lying down, or rolling a little. Pulse and respiration are normal. The problem may be mistaken for spasmodic colic because the pain is only moderate and there are increased intestinal sounds.
But as pressure builds up in the blocked tract, the pain increases. The horse becomes depressed, sweats a little, and may roll or thrash on the ground. Abdominal pain becomes severe and continuous, with pulse, respiration, and temperature above normal. Abdominal sounds cease and the stomach may fill with bloody fluid. The horse often dies within 48 hours of the beginning of this type of colic. Horses with acute intestinal obstructions (such as a twisted intestine) may show similar symptoms, but go into shock (due to blocked intestinal blood vessels from the twist) and die more quickly.
Impaction of the ileocecal valve (between the small intestine and cecum) and impaction of the cecum are both very serious problems. The horse usually needs sedatives to keep from thrashing and hurting himself. Removal of the obstruction is essential, but this is very difficult and often impossible without surgery. Surgery has a low success rate in these instances because the horse may not survive the operation, and if he does, it may be difficult to get the tract working again afterward.
In this type of impaction, mineral oil is usually given (2-to-4 quarts), followed in several hours by a drug to stimulate the intestines to try to get things moving again. The stimulation causes pain and there is a chance the intestine will rupture. Mineral oil should always be given first, to soften up and lubricate the packed intestinal contents.
Large intestine impaction
Impaction of the large intestine is more common, generally not as serious, and treatment is usually more effective. Large intestine impaction causes moderate pain, constipation, sluggishness, and lack of appetite. Rectal examination by a veterinarian usually reveals firm enlargements of intestine in long columns, and a rectum full of dry, hard fecal balls.
Causes of large intestinal impaction include the eating of coarse roughage or bedding, overeating (especially if a horse is fed irregularly with long intervals between meals), poor chewing, or lack of water. Fat, overfed horses are more likely to become impacted than horses fed moderate amounts. Horses brought off green pasture and into stalls or paddocks may develop impaction from overeating dry hay or bedding. Many horses will eat straw if it is harvested a little green or still has some grain left in it. Dehydration (lack of fluid in the digestive tract) can also cause impaction, as when horses do not drink enough water during cold weather or when water sources freeze up and they have to rely on eating snow at pasture. Horses that are finicky about drinking strange or muddy water may become impacted if they refuse to drink enough.
Other causes
Other causes of impaction are debility (due to lack of intestinal muscle tone in the sick or exhausted horse) or internal parasites that interfere with the local blood supply to the intestines resulting in sluggish intestines, impaction, and constipation. Fiber balls or enteroliths (mineral stones that build up around a foreign body) can obstruct the large intestine, causing recurring attacks of colic. Foreign bodies such as pieces of rope, plastic, or rubber (if a horse chews on coated fence wire, rubber feed tubs, etc.), can also cause blockage and impaction. Horses on dry feed are more likely to develop impaction than are horses on green pasture or alfalfa. Green feed and alfalfa stimulate intestinal motility and looser bowels.
Continued overloading of the cecum and large intestine causes the food to take too long to travel through the gut. Most of the moisture is drawn out of the food because it is in the intestine too long, and the dry, hard balls cause more problems, making it even harder for the intestine to move them along. If this happens for any length of time, the large intestine becomes insensitive to stimulation. Usually a full, distended feeling causes the intestine to contract and move the fecal material on out of the rectum, but if the gut becomes insensitive to this stimulation, it does not move, and the result is chronic constipation. In horses, the effects of impaction are more serious than in other animals because of the tremendous capacity of the large intestine.
Fecal material gradually accumulates in the large intestine until there is enough distention to cause pain and colic. Moderate abdominal pain may continue for three or four days or even a week or two. The horse is not violent and bouts of pain are moderate (the horse may stretch, lie down, or show other signs of mild discomfort) at intervals of up to 30 minutes. He has no appetite, but may drink water. Manure is passed infrequently in very small amounts and is hard and covered with thick, sticky mucus. If blockage is due to enteroliths, no manure is passed, and intestinal sounds are absent or much decreased.
Impaction of the cecum is hard to correct and may prove fatal, but most cases of large intestine impaction due to feed buildup or not drinking enough water respond well to treatment. If a horse dies from impaction of the large intestine, it is usually because the over-distended gut ruptures, or the horse becomes totally exhausted from a long course of impaction and colic.
Treatment
The best treatment for large intestine impaction is to give 2-to-4 quarts of mineral oil by stomach tube (and a gallon or two of warm water also, if the horse is dehydratedto soften up the mass of feed in the gutwater by stomach tube will soften up a dry mass better than mineral oil). If the problem is not relieved within 12 hours, more mineral oil and water should be given, and in some cases the veterinarian will give an injection to stimulate the intestines. Many cases will respond to one dose of mineral oil, but some will require a second dose. Impaction of the cecum may not respond, and in these cases a small amount of warm mineral oil may have to be injected directly into the impacted cecum through the rectal or abdominal wall.
Prevention is always preferable to treatment. Chances of impaction are greatly reduced with good managementby feeding quality hay in moderate amounts on a regular schedule, keeping horses free of worms, and making sure they have plenty of clean water. Older horses may need regular dental care. Greedy horses that bolt their feed should be fed small amounts frequently, so they do not overload the digestive tract. Highly palatable feeds such as lawn clippings should be fed sparingly or avoided altogether. Avoid coarse feeds, watch out for bedding eaters, and make dietary changes gradually (from hay to grass, grass to hay, etc.).
If a horse shows signs of abdominal discomfort, consult your veterinarian to help properly diagnose and treat the problem. A rectal exam can often reveal which area is impacted, and the horse can be treated accordingly.
