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Equine Colic

Colic is one of the most dangerous and costly equine medical problems, estimated to occur in 1 of every 10 horses each year (Tinker et al., 1997), it is the number one killer of horses. It is not a disease but a combination of signs that alert us to abdominal pain in the horse. Colic is a general term indicating abdominal pain. (n.) Spasmodic pain in the horse, usually caused by spasm of the intestine; (v.) The reaction of a horse to abdominal pain, kicking, rolling, sweating. The digestive system of a horse is a complicated series of interactions among many different organs. The small intestine alone is 60 feet long in your average size horse. Equine Colic can originate from the stomach, the small intestine or the large intestine. The entire digestive network is suspended and nourished by a thin membrane called the mesentery. Any malfunction, displacement, twisting, swelling, infection, or lesion of any part of this complex body system is what we recognize as colic. There seem to be countless situations which can precipitate colic. Many conditions causing colic become life-threatening in a relatively short period of time.

Because of the organs involved in colic, there are many types of causes of colic.
 
The Organs Involved in Colic

 
 
 

A. The horse's small, one compartment stomach.
B. Small Intestine
C. Cecum 
D. Colon 
E. Small Colon
F. Rectum

The main causes of colic are intestinal distension and reduced blood supply to the intestinal tract. Peristalsis (the waves of contractions along the muscular walls of the intestine that propel the contents along ) of the intestine is reduced and distention will occur due to reduced movement and absorption of water and nutrients. The pressure which results from this lack of passage of material through the digestive system results in a reflex action, which causes adjoining areas to contract in spasm. Distension and reduced blood flow may be due to an accumulation of gas fluid or feed, digestive disturbances, intestinal obstructions, internal parasites, or twisted intestine (torsion and volvulus).  Chronic distension may be caused by a horse constantly swallowing air "wind sucking".

The primary causes of the abdominal pain is the distention of the stomach or intestines, pain is also produced when the peritoneum is stretched during attacks of colic. The first response the body makes to distension is to INCREASE the secretion of digestive juices, which increases the pressure, and causes dehydration and imbalance in the chemical systems of the body. This can often become a feedback reaction which can lead to shock , which must be treated as a separate syndrome by the vet, since it is frequently the cause of colic deaths. The paralysis of the intestine also allows toxic material to escape through the stretched walls and enter the abdominal cavity, where the horse can be poisoned by his own intestinal contents.

 

Signs of Colic will vary according to the severity of the particular conditions. In the horse, abdominal pain is usually sudden. Very few horses exhibit all the signs at one time. Signs associated with mild to moderate pain include:

With more severe, unrelenting pain, horses may: A horse showing severe signs of colic should be seen by a veterinarian immediately. If the signs of pain are acute and the cause of the distention is not removed, death often occurs within 12 to 48 hours. Rapid diagnosis and treatment are vital. In cases of mild pain, the veterinarian should be consulted as to the best course of action. Be sure to give the vet your horses symptoms when you call,  put the horse in a comfortable stall and remove his feed and water. Allow the horse to lie down if he appears to be resting. If the horse wants to roll or is behaving violently, attempt to walk him slowly. Don't try to treat the horse CALL YOUR VET and be prepared to provide the following information: Along with any other symptoms noted above. Avoid administering drugs because certain drugs can mask clinical signs of colic, making an accurate diagnosis difficult. A horse does not need to be walked constantly if it is lying quietly and not attempting to roll or to continually get up and lessen his chance of survival if surgery is required. Walking the horse 15 min out of one hour is recommended by many Vets.

Diagnosis

There are various causes of colic and since the prognosis and treatment varies greatly with each, early recognition and accurate determination of what type of colic the horse is experiencing is very important.

Veterinarians often perform a rectal exam, intestinal contents and their position can indicate to the Veterinarian presence or absence of intestinal motility and the location of the obstruction or impact. A stomach tube may be passed, stomach contents or gas can help the Veterinarian decide the type of disorder and the severity of the condition. Other symptoms your vet will note include pulse ( rate should be less than 80 per minute for a favorable prognosis), temperature, presence or absence of intestinal sounds. Generally, the prognosis is excellent when pain is due to excessive activity of the intestines, good for pain due to impaction, and very poor for pain caused by twisting or intusssusception of the intestines ( unless surgery is immediate).

Some Causes of Colic

There are several nutritional aspects of colic which can be managed, thereby reducing the incidence of colic.

Digestive colic may result from:


Intestinal obstructions may result from sand impaction, retention of the meconium in foals, foreign bodies, and impactions caused by poor quality hay. Horses kept in sandy environments and fed on the ground or over grazed pastures are prone to consume more sand, predisposing them to sand impactions. Foreign bodies consumed by the horse may provide a nucleus where minerals are deposited until a large foreign body is formed. This foreign body is often referred to as enterolith (intestinal stone).  Mature, highly fibrous hay has been implicated in impaction colics. Water deprivation and stagnant warm water may contribute to impactions.

Parasitic load has long been stressed as a potential cause of colic. Internal parasites, especially Strongyles, cause severe damage to the intestinal arteries, reducing or blocking the flow of blood to segment of the intestines. Migration of larvae in the walls of the arteries causes the walls of the vessels to become roughened and scarred. Clots form on the roughened areas and may reduce the size of an important branch of the artery. Ascarids (roundworms) may cause blockage of the small intestine in young horses. Bots in large numbers may cause blockage of the stomach. Therefore, it is recommended that horses be maintained on a regular deworming program tailored to their individual parasite load.

Twisted intestine is a condition in which a portion of the small or large intestine is twisted on itself partially or completely. Twisting may result from rolling or from another cause such as a buildup of gas causing the distended intestine to twist. There is no simple cause effect explanation of colic, because many of the effects on the stomach, small intestine and large intestine are related. For example, blockage or impaction at the junction of the small and large intestines may be due to reduced blood flow because of strongyle larvae migration or due solely to sand impaction.

Diet and Management

Anatomically, horses have developed a specialized digestive system which allows them not only to survive, but also to thrive on high fiber diets   Studies have shown a decreased likelihood of a colic problem if horses are allowed to graze. However lush, high moisture spring pasture can also be a colic risk in horses. Colic problems in horses consuming large amounts of high moisture, low fiber grass virtually disappeared when horses were offered dry hay while grazing these pastures. Therefore, from a colic management standpoint, it is recommended that horses have access to pasture whenever possible, and be provided with additional dry hay when pastures contain a high moisture and a low fiber content (lush spring pasture).

Since horses are anatomically designed to digest fiber, the addition of grain concentrates to the diet is a potential risk factor for colic. Normally, grain concentrates contain large amounts of starch that are absorbed in the small intestine. Starch which is not digested in the small intestine spills into the large intestine where it is fermented by bacteria. One of the end products starch fermentation is lactic acid, which irritates the gut lining and decreases intestinal pH. The increase in acidity causes other more prevalent bacteria to die and release potentially fatal endotoxins. All of these situations can potentially cause the horse to colic. Using processed grains ( Steam crimping/rolling and grinding or pelleted), limiting the amount of grain provided in a single meal and the use of dietary fat as an energy source  to reduce the amount of grain concentrate needed in the diet all will help reduce grain induce colic.

Horses confined to stalls have an increased likelihood of colic (Reeves and Salman, 1993).  First, horses are designed by nature to consume forage in a continuous manner; however, stalled horses are routinely fed their hay and grain in two distinct meals (morning and evening). Second, stalled horses may not be receiving adequate forage to maintain proper gastrointestinal function. This may be especially true for horses being fed alfalfa hay. Alfalfa hay typically contains more calories per pound than grass hay. Therefore, horses fed alfalfa would be provided fewer pounds of hay per day than horses consuming grass hay. Not only are horses fed alfalfa receiving fewer pounds per day, reducing the amount of time spent eating, but alfalfa hay also contains less fermentable fiber than grass hay. The quality of fiber fed can also influence colic potential. Moldy hay, hay containing blister beetle contamination and hay with low digestibility can contribute to instances of colic. Since horses seem to have an absolute requirement for forage in the diet to prevent colic, it is recommended that a minimum of one pound of dry forage (hay/pasture) per 100 pounds of body weight per day is provided. For horses confined to stalls, the selection of lower calorie hays (grass type) will provide the horse more pounds of hay and mimic the continuous feeding behavior during grazing.
 
 

You can keep incidence of colic to a minimum by following sound management practices such as:

Colic will probably never be totally eliminated; however, the severity and incidences can be reduced.
© Beverly J Whittington 1998, 1999, 2000, 2001