Colic: To Walk Or Not To Walk

There are a number of things that can send shivers of fear running up and down a horse owner's spine. You walk out to the pasture and see your favorite mount standing there three-legged lame, blood dripping from a gaping wound in the leg being held aloft. Serious injury. You walk into the stable and there in that comfortable box stall is a horse rocking back on its rear legs, front legs extended. The horse is in obvious, severe pain. Laminitis. You walk into barn or pasture and there on the ground lies your horse, writhing in agony, its eyes glazed with pain, its coat dirty from rolling. Colic.

How the horse owner reacts in the above three situations can be critical to the animal's survival. In two of them, the action taken by the owner is pretty clear-cut. In the third, colic, there is a good deal more confusion.

The first step, of course, is obvious. Immediately call a veterinarian. What one does while waiting for the veterinarian to show up can be a little confusing when dealing with colic. That is not the case when dealing with serious injury or laminitis. In those two instances, one wants to keep the horse quiet and not moving. In the case of a bleeding injury, one should staunch the flow of blood.

But what about colic? Should you walk the horse until the veterinarian arrives? Should you put it into a corral and use a whip to keep it at a trot? What if it wants to lie down and roll? Should that be permitted (can't horses twist their gut if they roll?), or should the horse be kept on its feet?

Unfortunately for the horse owner, there are no clear-cut answers to most of these questions, only some guidelines. The reason for the confusion is that colic is not a single affliction. The word is used to describe abdominal pain in the horse. There can be many reasons for the pain and, until one knows the cause, it is difficult to decide what approach to take until the veterinarian arrives.

The universal remedy in years gone by was that the horse should be walked until the pain went away. There have been countless incidents where horse owners have walked and walked and walked. Then, they walked some more, until both they and the afflicted horse were ready to drop from exhaustion. Yet, the horse still suffered from colic.

The reasoning was that if the horse kept moving, it would aid in peristalsis—the movement of food through the animal's digestive system. Researchers are no longer quite so sure that this is true; walking might not be providing a digestive assist.

When food fails to move through the horse's digestive system, impaction colic often is the result. The causes can be many and varied. To understand how and why impaction occurs, we must understand the horse's digestive system and its eating habits.

The horse was designed by nature to exist on forage. It is a grazing animal. If left to its own devices on open range, the horse will eat a little food many times per day. It will graze leisurely until its hunger needs are satisfied, then will perhaps take a long drink, followed by a doze in the sun for an hour or two before leisurely grazing some more.

By eating in such a manner, the horse allows its digestive system to move continually and process the food that has been consumed. The prime area for processing forage is the large intestine. The digestive process involves a form of fermentation where fibers are broken down, nutrients extracted, and waste moved along preparatory to excretion.

It is not the most efficient of processes when compared to ruminants, where digestion of forage takes place in a large compartment of the stomach known as the rumen. The rumen is like a large fermentation vat, while the large intestine is a huge tube that is looped around inside the abdominal cavity.

As long as the horse's digestive system proceeds in a normal manner, all is well. During the process, gas and liquids are produced and are moved along through the system. By pressing your ear against a horse's side or using a stethoscope, you can eavesdrop on this process. When all is routine and normal within the digestive system, there will be a gentle gurgling and rumbling from within.

Unfortunately, things are not always well within the equine digestive system. One of the problems that can occur involves a halting of the food movement process. This is impaction, and it might occur at one of the bends in the large intestine. As the term implies, impaction occurs when a mass of partially digested food blocks an area of the large intestine, making it impossible for the food being processed behind it to continue moving. The result usually is colic.

There are many causes of impaction, but rarely are grass and leafy green hay involved. Forages that would be more apt to cause impaction would be those of high fiber content, such as straw or corn stalks, which the large intestine would have difficulty breaking down. Certain ground feeds that are ingested without adequate water intake also have been implicated. Impaction can be the result of ingested sand as well.

When impaction occurs, there is a cessation of gut sounds. When you press your ear against the animal's side, there will be silence or near silence instead of the normal gurgling and rumbling.

As with so many equine maladies, prevention is far better and often easier to accomplish than effecting a cure. The owner should make certain the horse has plenty of the right kind of roughage in its diet—either leafy green hay or grass—and that it has constant access to water. It stands to reason that if a horse eats small amounts of food frequently, it also should be ingesting water frequently. Concentrates should be fed in small amounts frequently, rather than in a large quantity once per day.

When impaction is suspected, one should call a veterinarian immediately. While waiting for medical help to arrive, one should walk the impacted horse quietly. The activity should do no harm and might help to take the horse's mind off its discomfort.

The veterinarian might administer mineral oil or other substances in an effort to free the blockage, but it would not be something the layman should attempt. Normally such fluids are administered via a stomach tube inserted through the nose. This method would require professional help.

Grain Overload

The horse's digestive process also can get totally out of synch when the animal gets into the grain bin and ingests far more of the potentially volatile food than its digestive system can accommodate. This is another of those situations that send shivers of fear up and down the spine. You walk out to the barn in the morning and notice that the horse's stall door is ajar. Then, with a sinking feeling, you find the horse at an open grain container and realize that the animal has perhaps eaten a week's supply or more.

The stage is set for a form of colic, if it hasn't already occurred. If it hasn't, the horse owner's first move should be to call the veterinarian and not wait for the first signs of colic. Overeating of grain also can result in laminitis, so early treatment is imperative.

Waiting for the veterinarian to arrive might be the time when walking would be advised in the hope that it would assist in keeping the digestive processes working. Besides, it gives one something to do other than just sit idly and stare at the horse while waiting for the veterinarian.

What should not be administered at this point is water. That will hasten fermentation and compound the problem.

Several things happen when a horse ingests too much grain. The digestive process in a horse produces substantial quantities of gas and fluid. When gas and fluid are produced more rapidly than the body can eliminate them, there is distention of the stomach or intestine. Distention causes severe pain. The most serious distention is that caused by gas.

Ingestion of large amounts of grain also leads to the release of toxins from dying bacteria, and these toxins can cause a number of complications, including founder and even death.

Prevention of this form of colic, of course, is far better than any treatment. Stall doors should contain latches that the horse can't open and all grain containers should have covers that can be securely fastened.

Spasmodic Colic

Perhaps the most common colic is spasmodic colic, which is due to muscular spasms of the intestinal tract. It is similar to simple indigestion in people. However, it can be very painful to the horse and can be brought on by over-excitement which causes the release of hormones that can interfere with the normal function of the digestive tract.

Another anecdote. At one time we had a nice grade mare we used for a pack animal. The only problem was that she would colic after being unloaded from a trailer in the wake of a trip to a mountain trailhead.

The first time it occurred, we had traveled only about 100 miles from our home in Wyoming to a trailhead in the Bridge-Teton National Forest. It was to be a new experience. We arrived at the trailhead in the evening. There were a clear sky and a full moon, so we decided to ride to our first campsite, only a few hours' ride away, by moonlight.

The young mare stepped off the trailer and almost instantly cramped up. Colic. She didn't seem to be impacted, so we assumed it was a case of spasmodic colic. We walked her around a bit, but the pain seemed to get worse rather than lessen. We had some Banamine in our first-aid kit and administered it intravenously.

This procedure would not be recommended if you are at home waiting for the veterinarian to arrive. First, of all, he or she might decide it was not the appropriate drug under the circumstances and, second, it could mask symptoms and make it more difficult for the veterinarian to arrive at a correct diagnosis.

However, colic usually does not strike under the best of circumstances, and when that is the case, the horse owner must make use of options that are available.

In our case, the Banamine did the trick. The mare soon was standing quietly and shortly thereafter was cropping grass. By then, however, the moonlight ride didn't seem like such a good idea. What if the mare became ill again when the effects of the pain killer wore off? We were many miles from veterinary help as it was. We didn't want to compound the problem by riding into the wilderness. We camped overnight at the trailhead. The mare was fine the next morning and throughout the trip.

Unfortunately, the next time we hauled her, the same thing happened. Again, Banamine solved the problem, but by that time, we were worried that we were dealing with a chronic situation. At present the mare makes her home with folks who don't require that she travel.

The "Twist"

One of the most insidious forms of colic is the twisted intestine. As already mentioned, this is a form of colic where no amount of walking will help. The only remedy is surgery, and even that must be performed quickly if the horse is to survive.

Although there has been a great deal of research on the subject, no one is quite sure exactly what causes a twist. For years, horse owners thought that it resulted from a horse's rolling on its back. Researchers have found that this is hardly ever the cause. Many horse owners have whipped their horses to their feet during bouts of colic, fearing that rolling will result in a twist. Research has shown that if a twist is involved, it usually has occurred before the horse ever lies down and rolls.

Nature didn't seem to do the horse any favors in designing the large intestine, which is actually a gigantic tube. In order to fit into the horse's abdomen, the large tube is folded into several sharp bends where food can become impacted and where the intestine can get out of place or twist.

One twist that is commonly encountered is known as large colon volvulus (LCV). It can be treated surgically. This was the subject of a report presented at the 1996 American Association of Equine Practitioners meeting by Rolf M. Embertson, DVM, Dipl. ACVS, of Rood and Riddle Equine Hospital in Kentucky.

Perhaps the point driven home most emphatically by Embertson was that early detection of the condition and immediate surgery are key in determining whether the horse will survive. In other words, if the condition occurred and the owner persisted in walking the horse for hours on end before seeking help, the outcome of surgical treatment would be severely compromised.

Embertson told his audience that medical records of horses requiring colic surgery at Rood and Riddle Equine Hospital from March of 1986 through February of 1995 were reviewed, and those of horses with LCV were closely examined. During that time frame, he said, 897 colic surgeries were performed on 828 horses. Seventy-one percent of these horses survived and were discharged. Broodmares comprised 79% of the total case load of surgical colics. (Broodmares are a large portion of the horse population in the area.)

Of the total number of colic surgeries performed, 238 surgeries on 204 horses were performed to correct large colon volvulus.

Embertson had this to say in his report:

"Eighty-three percent of horses requiring one surgery for LCV were discharged from our hospital. Eighty percent (28 of 35) horses with LCV that had an additional surgery for LCV or right dorsal displacement of the large colon survived the second surgery. One hundred percent (two of two horses) with LCV that had a third surgery survived the third surgery.

"The mean duration of illness before presentation was 4.2 hours for survivors and 6.2 hours for non-survivors. The volvulus (twist) was 360 degrees in 68% of the LCV patients, comprising 68% of both the survivor and non-survivor groups. The volvulus occurred most commonly at the base of the cecum when recorded, and 97% occurred in a counterclockwise direction as viewed from the ventrum."

When one studies the above figures, it becomes readily apparent that there is a narrow window of opportunity if a successful surgery is to be performed.

Embertson had this to say in conclusion:

"The shorter duration of clinical signs prior to surgery and an improved survival rate found in this study strongly support the necessity for immediate surgical intervention for LCV."

When foals are involved and surgery is necessary for colic, the prognosis becomes more guarded. Presenting a report at the same conference on the subject of colic surgeries on foals was N.J. Vatistas, BVSc, University of California, Davis. Vatistas reported on a study that involved 67 foals which underwent abdominal surgery for colic at the Davis veterinary hospital. The surgeries occurred between the years 1980 and 1992.

Overall, of the 67 foals in the study, 29 survived longer than two years. Thirty-two were euthanized or died, and six were lost to follow-up.

"Only 19% of the foals with strangulating intestinal lesions survived, in contrast to 69% with non-strangulating intestinal lesions," Vatistas reported. "In addition, younger foals appeared to have a poorer prognosis for survival than older foals."

Another study reported at that conference also indicated that older horses have a good chance for survival if the surgery is performed early. Presenting this report was Suzann A. Carson-Dunkerley, DVM, of the Auburn University College of Veterinary Medicine.

Examined in the study were the medical records from 104 horses of 17 years of age or more which were treated at the veterinary hospital for acute abdominal disease from December 1990 through February 1996.

Breed representation was as follows: 31 Quarter Horses, 19 Thoroughbreds, 17 Arabians, eight Tennessee Walking Horses, seven gaited horses, six ponies, five warmblood mixed-breed horses, four draft horses, three Morgans, and four of other breeds.

Carson-Dunkerley had this to say about treatment and its outcome:

"Fourteen of the horses were euthanized after examination without further therapy at the owner's request. In seven cases, the owner's presenting complaint of colic was not related to gastrointestinal pain. Diagnoses (for those cases) included thoracic neoplasia in two horses and one of each with liver disease, pharyngeal disease, choke, ruptured spleen, and uterine artery rupture.

"Surgery was performed on 32 horses. Eleven of these horses were euthanized during surgery because of necrotic or ruptured bowel. Twenty-one horses recovered from anesthesia. Of those recovered, 16 were discharged from the hospital. Of all 32 horses taken to surgery, including those euthanized on the table, 16 were discharged from the hospital."

So, Walk Or Not?

What the above studies tell us is that when colic surgery is required, there is a good chance for a successful outcome with mature horses if the animal is presented for surgery when the affliction is in its early stages. Thus, we come back to the point that getting a veterinarian on the scene early is imperative. A matter of only a couple of hours can be of utmost importance if surgery is required.

In other words, if the horse requires surgery and we insist on walking it for several hours before calling for medical help, we might literally be walking the horse to death.

When considering the question of whether to walk the horse or not to walk it, we might make the comparison with a person who has severe abdominal cramps. The last thing that person would want to do would be to walk about. Instead, he or she would try to find a bed to lie on and to assume a position that provides some degree of comfort.

In essence that is what the colicky horse is attempting. It is seeking a position where the pain is alleviated and there is a degree of comfort. What this means in practical terms is that if the horse with colic is lying quietly, whether on its side or sternally, it is best to let it be.

We must remember that some colics are of long duration with debilitating pain. This means that the horse will need all the strength and stamina at its disposal to fight its way through the affliction. Walking it endlessly can tire the horse and sap its energy.

On the other hand, if the horse is rolling about violently, that action might sap its energy even more than walking. Getting it on its feet and moving might actually result in conserving energy. In addition, when the horse is rolling, there always is the danger that it could injure itself by getting a leg caught in a fence or under a stall door.

Once the horse is on its feet and walking, there is no need for speed. Sending the horse careening around the arena or corral at a run doesn't help anything. It merely uses up the animal's energy more quickly. Walking the horse slowly and quietly is far better than forcing it to move at speed.

Dwight D. Bennett, DVM, Colorado State University, who has authored papers on colic, had this to say in one of his papers:

"Despite what has been passed down through the years, it is acceptable for a colicky horse to lie down. Furthermore, it is considered unlikely that the horse will twist the intestines by rolling. In fact, lying quietly may be good for a colicky horse, because the more energy he uses in kicking, pawing, and rolling, the more rapidly he may go into shock, which is a common cause of death in colicky horses. If the horse rolls violently, he should be walked very slowly. Do not beat the horse to keep him on his feet or keep him moving."

Earlier we mentioned that surgery often is successful in certain types of twists and displacements if the horse is presented for the operation during the early stages of the affliction. Unfortunately, there is another element involved.

Cost

Colic surgery is quite expensive because it is major surgery. The horse owner must often make an agonizing decision between surgery and euthanasia, with financial resources being part of the consideration.

So, this discussion concerning whether to walk the colicky horse has come full circle. There is no single, simple answer. It all depends on the circumstances. The only clear-cut conclusion is that veterinary help should immediately be sought when colic occurs or when an onset, because of undue grain ingestion, is believed to be imminent.

~~ BACK TO TOP ~~

The lulling sound of waves slowly rolling in and out. A nice, sandy beach. Great scenarios vacation-wise, but a crisis in the making when applied to your horse's gut sounds and abdominal radiographic post cards. Diagnosis: Sand colic.

Sand colic occurs when the horse ingests sand along with regular rations into the intestinal tract. "Sand colic is typically seen in horses that live in dry, sandy areas," says Andie Dee, DVM, of B.W. Furlong and Associates in New Jersey. "You can't always hear sand when it's in the intestinal tract, but when you do, you'll never forget it," Dee says. "It sounds like the tide rolling in and rolling out."

"Sand colic is abdominal pain caused by an intestinal obstruction, i.e., an impaction," states George Martin, DVM, Dipl. ACVS, and Professor and Section Chief Equine Medicine and Surgery, Louisiana State University. "In most impaction colics, the obstruction is caused by feed, but in sand colic it is caused by sand."

Dee says that some horses seem to be more prone to sand colic than others, even when sharing the same environment. "We don't know why. It may have something to do with the ability of an individual's intestinal motility to keep things moving along. Or, it may be that one individual tends to pick up more sand than another."

While age is not a factor, weanlings, yearlings, and sometimes nursing foals are more inclined to eat sand preferentially, points out Terry Swanson, DVM, CEO of Littleton Large Animal Clinic in Colorado and a former president of the American Association of Equine Practitioners.

Abdominal distress is the most common clinical sign of early stage sand colic, just as it is for a mild "regular" colic. "There is no clinical sign specific to sand colic," Martin says, "but some horses will develop diarrhea as the primary sign or just before the signs of colic develop." Typically, the horse suffers from inappetence and abdominal pain. The animal also shows signs of being mildly depressed and/or sweaty, has a fever, yawns excessively, adopts a posture to urinate but fails to or urinates very little, looks at its flank or belly, lies down, paws, rolls, or thrashes.

Diagnosis is based on tests, clinical signs, and observation of the environment.

"From a veterinary standpoint, we'll look at the environment," explains Swanson. "Is the horse in a sandy corral or pasture where sand is readily available? Is the horse being fed in an environment where he's picking up feed and sand at the same time? We look for that when trying to establish a diagnosis."

Stool samples are checked for sand. "We take the fecal material, add water, mash it up, then let it settle out for about 20 minutes," says Swanson. The manure "tea" can be mixed either in an ordinary bucket or in a rectal sleeve. If sand is present, it will settle out first because it is heavier. Take caution, however, for sand can be present in a normal horse's feces as well.

Abnormal abdominal sounds might point to sand colic, says Dee. "Typically when veterinarians auscultate (listen to) the abdomen, we listen to four quarters--the upper and lower sections on the right and left sides. But when we're looking for sand colic, we also listen to the ventral midline.

Martin explains how to listen for sand colic. "The process is to push abruptly and forcefully into the horse's lower abdomen with your fist, then listen for the peculiar sound of the sand particles moving in the large colon."

Sand also is visible via radiography. "We've X rayed some horses that looked like they had a little beach in the bottom of their large colons!" Swanson reports. Radiographing foals, miniature horses, ponies, and small horses generally is not difficult, but for full-sized horses, abdominal radiography is more difficult, says Swanson, because of the need for larger radiographic equipment.

Occasionally, the veterinarian might perform an abdominocentesis. "We put a needle in the bottom of the abdomen to check the peritoneal fluid surrounding the intestine," Swanson says. "If a horse has a bowel that is smothered with sand, sometimes you can feel sand on the needle. We don't like to use this procedure, but occasionally it is done."

Another diagnostic test is ultrasound. Using a probe along the ventral abdomen, you can visualize the sand as starbursts. There is research in progress at Auburn University exploring the effectiveness of ultrasound for sand colic diagnosis (see sidebar on page 78).

Treatment

"Conservative treatment is ideal when diagnosed early," Martin says. "Administration of a bulk laxative product, such as psyllium (Metamucil), appears to be the most effective. Psyllium is believed to work by stimulating intestinal motility and by agglutinating the sand (making it stick together), allowing the horse to pass the sand. Other laxatives such as mineral oil generally are ineffective because they tend to float over the surface of the impaction. Rehydration and over-hydration with intravenously administered fluids can help add moisture content to the lumen in the area of the impaction."

The impaction will cause many horses to become bloated because they cannot pass the gas. This usually causes severe pain.

Swanson says that antibiotics are sometimes added to the regimen to protect the horse from absorption of bacteria from a bowel that is inflammed by the sand.

"Over the course of several hours, if the horse's clinical signs do not improve, or if they worsen, then surgical exploration is the next treatment step," says Martin. "During surgery, the treatment is to remove the sand from the large colon. This can be done relatively easily, although there can be some tricky aspects to the procedure. Basically, the most moveable part of the large colon is withdrawn from the horse's abdomen and either placed on a sterile tray or hung over the edge of the table. A 15-20 cm incision is made into the colon, and the contents are flushed out onto the floor or into some type of collecting system. (The contents of the colon are filled with bacteria and must not be spilled onto the external surface of the colon or into the abdominal cavity because infectious peritonitis will be inevitable.) After the sand has been removed from the large colon, the incision in the colon is sutured, and the bowel is re-positioned in the horse."

Sand colic can be fatal when it is left untreated, if treatment is initiated too late, or when the condition is very severe. Sand colic usually is fairly mild and responds favorably to conservative treatment. Horses requiring surgery have about a 60%-65% survival rate, says Swanson.

Prevention

The threat of sand colic can be minimized in high-risk areas by taking a few preventive measures. Swanson offers some suggestions. "Observe your horse to see if he has habits that would cause him to ingest a lot of sand. In other words, is he always nibbling on the ground, rubbing his nose, acting like he's ingesting sand? Feed horses in an environment where the hay leaves fall on a firm surface other than sand. If you're feeding outside in a lot, arrange some way to have a harder surface where the feeder is. If feeding in a stall, lay down rubber matting where the hay is so the horse isn't picking the leaves up out of the sand."

"Allow horses to graze only in pastures with adequate growth so that ingestion of sand is less likely," adds Martin.

In addition, feed horses grain and hay before turnout, so they are not so hungry, and will not rip the grass up with the sandy roots. If possible, turn out horses in the day during the summer, so they will go into the woods and not eat so heartily.

Horses which live in a sandy environment or which have had sand colic before might benefit from preemptive measures via regular feeding of psyllium. "I recommend one to two cups of psyllium per 1,000 pounds of horse daily for a week, every four to five weeks," says Martin. Alternatively, Swanson notes psyllium can be fed one day a week, every week. "I don't recommend every horse that lives on a sandy lot be put on psyllium, but if a horse appears to be nibbling or licking the sand or a stool sample shows an impressive amount of sand when you float the stool, then that's the kind of horse I would put on a prophylaxis."

Swanson warns that psyllium should be fed intermittently, like once a week, rather than continually. "Bulk laxatives seem to have more effect that way," he says. "When used every day, the physiology may adjust to that, and we don't get the desired effect."

While complete control of the factors that cause sand colic aren't possible, smart preventive techniques can reduce the risk of your horse's developing this affliction. Prompt diagnosis and treatment can ensure that a mild colic doesn't become a fatal colic.

~~ BACK TO TOP ~~

There are moments spent with our horses that are often taken for granted: The welcoming whicker as you approach with dinner, the snuffling in the feeder for tasty bits and pieces, the melodic sound of chewing as your horse enjoys every morsel, and the sweet smell of hay as it is crushed between your horse's teeth. When these ritual sounds and senses of the day go missing, there is a sense of dread.

Your horse isn't interested in coming in for dinner. Out in the paddock, he is occasionally pawing the ground, half-heartedly. With a sigh, he plops to the ground, lying quietly. After a few minutes, that doesn't seem to suit him either. He rises, shakes his neck and head as if to throw off a cloak of discomfort, then stands despondently.

Although this presentation might be typical of a horse that simply isn't feeling well, it is also quite typical of a horse with intestinal discomfort from impaction colic.

What is Impaction Colic?

Impaction colic is caused by a blockage that forms due to feed material obstruction in the large colon. Nat White, DVM, MS, Dipl. ACVS, and Marco Lopes, DVM, MS, professor at the veterinary school in Brazil, have pursued colic research at the Marion duPont Scott Equine Medical Center in Virginia with support of the Grayson-Jockey Club Research Foundation. White, director of the Equine Medical Center, says, "Large colon impactions make up as much as 8-10% of all colic, but the cause in a large majority of the cases is not known. Nearly 30% of all equine colic cases at referral hospitals are attributable to an impaction."

As food traverses the digestive tract, it enters several segments of large colon that narrow considerably before opening into a somewhat wider portion of intestine. These narrow spots are more prone to blockages. Impaction can also develop in the cecum (less than 5% of all impactions) or in a portion of the small intestine leading into the cecum called the ileum.

An important function of the large colon is to provide a reservoir from which fluids and electrolytes are absorbed. Normally, 30-40 gallons of fluid are secreted daily into the upper bowel, with about 90% of this efficiently reabsorbed in the cecum and large colon. High-fiber diets composed of good-quality hay have the advantage of increasing colonic water by at least 30% over diets that are comprised of added grain products.

Motility of the large colon is best stimulated by the volume of food and water introduced to the intestines. Delay of movement through the colon causes more water to be absorbed out of the fecal contents.

Lopes and colleagues' study on gastrointestinal motility showed that, "Feed intake is a major stimulus for gastrointestinal motility, thus fasting leads to GI hypomotility (slow movement). Although fasting is unavoidable or even desirable in some situations, management practices to offer the opportunity for the horse to have a more continuous eating pattern best mimic natural conditions. Dehydration and electrolyte imbalances may also lead to GI hypomotility."

Dehydration causes drying of the colonic contents, and coupled with sluggish gut motility, there is potential to develop an impaction. Dehydration occurs subsequent to protracted exercise, intense sweating, inadequate water consumption, or hormonal changes. It can also occur when a horse doesn't drink enough due to frozen or polluted or contaminated water. Lopes says, "Preventing dehydration and electrolyte imbalance by providing continuous access to fresh water and feed (including a salt block) is indicated."

Effects of Feeding Strategies

Horses evolved to graze small amounts of fiber-rich plants for 13-15 hours a day, and this style of eating avoids overfilling of the stomach. In today's fast-paced society, horse-keeping must suit space and schedules. Not all horses have access to pasture, and not all horse owners can be present to feed small meals throughout the day.

Feeding large meals twice a day, particularly of grain, has profound effects on intestinal function. In a recent project by Lopes and White, the amount of water in the horse's colon was compared when feeding a hay diet or a diet of hay and grain.

"We hypothesized that increasing the grain would decrease the amount of water in the colon, perhaps creating the conditions for impaction," says White. Indeed, this is what was discovered, and it corroborated previous research findings: Horses fed a large grain meal twice a day experience a 15% reduction in plasma volume within 30 minutes of the meal. There is no change in plasma volume in horses fed smaller amounts of grain every few hours.

White elaborates, "Feeding grain decreases the amount of fiber in the diet, which decreases the water content of the colon and alters fermentation to produce more gas. The changes created by twice daily feedings of grain set up conditions for extremes in fluid exchange in the colon, which can dehydrate the ingested feed and potentially set up conditions that could lead to simple or severe colic."

For every pound of feed ingested, a horse needs two to four pints of water for digestion. This means a 1,000-pound horse consuming 20 pounds of food each day needs a minimum of 7.5 gallons (30 liters) of water to process the feed. This is the amount necessary solely for intestinal function; additional water is necessary for maintenance functions. Note that pelleted roughage requires more water for digestion, and it can to lead to impaction if water intake is restricted for any reason.

Dehydration of colonic contents is not the whole story. There are other important mechanisms that contribute to intestinal transit, such as viscosity of the food, diameter of the tube through which ingesta flows, and pressures within the intestine that progressively propel material towards the rectum while retaining them long enough to extract nutrients. In addition, offering a large meal only twice daily can interfere with the activity of intestinal microbes responsible for efficient digestion of fiber because of the change in pH that takes place when a horse digests food.

Overfeeding of indigestible material such as poor-quality hay is thought to be a significant contributing factor to the development of an impaction. "To prevent formation of ingesta that is too viscous (thick), it is better to avoid mature grass or any feed composed of poorly digestible fiber," says Lopes. "Whenever hay or grass is fed, the contents of the large intestine have two distinct phases: A solid phase, composed of undigested pieces of grass, and a liquid phase. This liquid phase is loose and can be moved independently from the solid phase, leaving behind a mass of solid particles that can form an impaction. If poor-quality roughage is fed, the properties of the solid phase change (i.e., larger particle size, increased particle stiffness) in a way that makes formation of a hard mass (an impaction) even more likely.

"Although not proven, there is evidence that poor dentition could also increase the risk of impaction by compromising mastication, which would lead to a situation similar to what is seen with ingestion of poor-quality roughage: Ingesta would be composed of larger particles. Thus, regular dental care is recommended," adds Lopes.

Lifestyle Effects

"Alterations in motility, water content within the colon, and changes in exercise are all considered as possible risk factors," says White of colic. "The problem appears more common in mares and middle-age horses. Events associated with the impaction include management changes within two weeks prior to signs. One of the most frequently reported management changes is sudden restriction of exercise due to a musculoskeletal injury, including hospitalization or restriction of exercise after surgery."

One study reported recent stall confinement was associated with 53.7% of impaction colic cases; another study found 62.5% of colon impactions occurred within two weeks of significant management changes, such as stall confinement or transport.

Confinement might have multiple adverse effects on equine intestinal function. Stalled horses often experience inconsistencies in feeding intervals and amounts relative to their previous management.

Lopes comments, "Ingestion of indigestible non-feed material such as shavings, sand, gravel, hard seeds (e.g., cockspur hawthorn, mesquite beans), hair, pieces of rope or twine, and pieces of rubber can also lead to GI impaction. Although most horses would not eat these materials, some may develop vices due to conditions such as prolonged stall confinement or hunger. Thus, the time horses are kept in stalls should be minimized."

White mentions concerns about diets fed to inactive horses: "Ideally, horses confined to a stall should not have any grain, as energy is rarely needed. Unfortunately, most owners or managers are not aware of the quality of hay they feed in terms of its energy and protein content." Hay should be analyzed for nutrients prior to being fed to the horse so a proper diet can be formulated to meet his energy requirements.

"During confinement or transport, use of bran mashes or other diet alteration has not been proven to prevent impactions, yet feed modifications add the risk associated with diet changes, which have been incriminated in causing colic," White adds.

Exercise provides multiple benefits by increasing metabolism and improving intestinal motility. White says, "Ad lib exercise is best for horses, as some exercise appears to favor the normal digestive process with frequent intake of small amounts of feed over time. Just as changing the diet can be a challenge to some horses' digestion, horses with acute decreases in activity should be monitored closely for digestive problems that can lead to colic."

Lopes concurs: "There is evidence light physical activity (i.e., walking) stimulates GI motility, so it is better to avoid maintaining a horse in a stall for long periods."

Fiber digestibility increases by up to 20% in exercised horses, promoting greater retention of the fluid part of the diet and shortened retention of the more formed, particulate part of the feed. Progressive movement of particulate materials down the intestinal tract promotes efficient digestion while not allowing it to linger to form dehydrated intestinal contents.

Feeding in the period surrounding exercise is not without problems. Rigorous exercise just prior to feeding can decrease feed digestibility while blood remains shunted to working muscles and away from the intestinal tract. White notes, "Strenuous exercise will shut down intestinal motility. Therefore, it makes sense not to have a large quantity of feed in the stomach or small intestine during exercise. Feeding forage at intervals during moderate or light exercise appears to be appropriate."

Proper measures should be taken to adequately cool out a hot horse before feeding large meals, particularly grain.

Other Causes of Impaction Colic

Sand ingestion also has the potential to create an impaction, particularly in the right dorsal colon. One of the best means of moving sand through the bowel is by promotion of active intestinal motility. Feeding a fiber-based diet that consists of at least 50% hay, roughage, and/or pasture keeps the intestines moving well and should encourage passage of small amounts of sand so it does not accumulate in the bowel. In some areas, psyllium is fed to help manage sand ingestion.

Coastal Bermuda grass (Cynodon spp.) common to the southeastern United States is known to elicit intestinal contractions around a mass of feed, causing more water to be compressed out of the material; this can lead to increased desiccation and firmness of the intestinal contents. Mature Coastal Bermuda grass has a high, non-digestible crude fiber content that increases its propensity to ileal impaction colic.

Tapeworm infestation has also been incriminated as a cause of ileal impaction. Lopes stresses that ivermectin does not affect tapeworms, so choose dewormers that specifically target tapeworms, such as a product that contains praziquantel.

Certain medications, such as phenylbutazone (Bute) and flunixin meglumine (Banamine), are often given to a horse for an injury or to reduce post-operative pain and swelling. Such non-steroidal anti-inflammatory drugs (NSAIDs) can contribute to the risk of cecal impaction by diminishing smooth muscle contractility (and thus motility) of the colon. Caution needs to be taken during a colic crisis to administer as little a dose of an NSAID as necessary so it will not mask clinical signs of a surgical colic condition.

It is this author's experience that significant orthopedic pain from hind limb injury or surgery is a risk factor in developing a cecal impaction. Lopes says, "The activity of the sympathetic nervous system
contributes to reduce GI motility. Thus, conditions (such as pain) that activate the sympathetic nervous system should be controlled."

Signs of Impaction Colic

Transit of feed through the large colon takes several days, so what passes as manure today was ingested at least three days ago. An impaction might take days to form and to reveal itself as a problem. It is not until a horse feels abdominal tension that he will show discomfort.

When pain does develop, it usually starts out as mild and intermittent. An affected horse might at first appear depressed. He might look at his flank, paw, stretch, kick at his belly, exhibit a flehmen response (curling the upper lip), or spend a bit of time lying down. He might still nibble at food, but he seems finicky. Manure production is scant or absent. Feces that pass are dry and diminishing in quantity. The feces of a stagnant bowel might be coated with mucus and fibrin strands in the body's attempt to lubricate dehydrated fecal material. A normal horse will pass eight to 12 bowel movements in a 24-hour period; it is helpful to know what is normal for your horse, as this varies among individuals.

With a simple obstruction that's detected early, the horse's heart rate, temperature, and other vital signs are usually within normal limits, but the respiratory rate might accelerate relative to the degree of pain. The body's attempt to correct the blockage can create a hypermotile gut with active and noisy intestinal sounds in an attempt to squeeze the impaction through the bowel. These sounds can be misleading since not all intestinal activity results in progressive movement of material.

As a horse's status deteriorates with an unrelieved impaction, there is increasing distention and pressure on the bowel, and lessened blood flow to (and degeneration of) the intestinal lining. White suspects a link between colon displacement and a preceding impaction: "At surgery, many displacements have a colon filled with ingesta. Some appear to be impactions and some appear as increased ingesta."

The degree and frequency of pain will continue to worsen over time in a surgical case. Intestinal sounds and activity might cease (called ileus), which is dangerous.

Effective Treatment

"The basic premise for treating colon impaction is relief of pain, softening the consistency of the impacted ingesta, and stimulating motility to increase fecal transit," says White

An effective strategy uses overhydration via an IV. Overloading the blood vascular system with fluid increases secretion of intestinal water into the impaction to soften it, while also maintaining whole-body hydration and circulation to intestinal blood flow. IV fluid treatment might require 40-80 liters per day. Once the horse is hydrated, administration of a balanced electrolyte solution by stomach tube at a rate of 5-10 liters per hour helps hydrate colon contents and has been effective in treating horses with impactions.

Pain-relieving medications elicit smooth muscle relaxation of the intestinal wall, thereby minimizing spasms that tighten the intestine around an impaction and allowing gas and fluid to pass. A trailer ride or walking can be beneficial to evacuate gas and to stimulate intestinal motility.

It is important to stop a horse's food intake; more food might add to the size of an impaction. It might be necessary to apply a muzzle to prevent eating as he starts to feel better. White says, "Research suggests that colon hydration is increased when fasted horses are fed hay. Although feeding can increase motility and oral water intake, feeding horses with impactions should be delayed until there is evidence that the impaction is moving or is resolved. When initiating feeding after the impaction has moved out of the colon, a laxative diet without grain, such as grass or alfalfa hay, is preferred. Use of bran as a laxative should be avoided. Although pure bran is high in fiber, most milled bran contains large amounts of carbohydrate, which reduces total fiber content and potentially decreases colon water content."

Short periods of grazing might be helpful for its laxative action and high water content. Avoid overconsumption of grass as it is highly fermentable and might contribute to gas distention of the bowel.

The majority of impaction colics respond to medical treatment. Although called a simple obstruction, some impactions might not be resolved even with intense medical management or IV fluid therapy. Ongoing deterioration can necessitate surgical intervention due to a concurrent problem such as displacement of the intestinal loops or compromised bowel circulation. Obstruction of the large colon that persists for more than 24 hours might have an adverse effect on intestinal nerves, predisposing a horse to future impaction colic from a lack of nerve stimulation of muscles along the gastrointestinal tract. Rapid identification and resolution of an impaction is key to a successful outcome.

White says long-term survival for horses treated medically (95.1%) was much better than those treated surgically (57.9%).

Take-Home Message

"Optimally, horses should be fed a diet with a minimum of 60-70% forage," says White. "This means feeding only pasture or hay, and only feeding grain when necessary. High-quality hay will provide adequate protein for most horses. The horse's intestine doesn't always tolerate acute changes in diet, so when a change is necessary, the transition should be made over time, normally seven to 10 days."

~~ BACK TO TOP ~~

BACK