The word colic sets a horse owner’s heart racing like almost no other word. It is scary to see your equine friend so distressed and uncomfortable. While most colics are mild and can be treated on the farm, other colics can be live threatening and may require intensive treatment or surgery. Some can even be fatal. The word colic simply means abdominal pain. The gastrointestinal tract of the horse is large and varied with lots of places for a problem to develop. Thus there are many causes of colic. When your veterinarian evaluates your horse for colic, one of their goals is to determine the reason your horse is experiencing abdominal pain and to try and differentiate the mild cases from those that need more intensive care. In this multi-part series on colic, we will be discussing the anatomy of the horse intestinal tract, different causes of colic, and different treatments for colic.
PART 1: ANATOMY OF THE EQUINE GASTROINTESTINAL TRACT
The horse has a large and varied gastrointestinal tract. Some portions of the tract are similar to ours and other portions are very different. Horses chew their food in their oral cavity or mouth. Once they swallow, the food travels down the esophagus to the stomach. Horses have a stomach that is fairly similar in function to ours. It is about the size of a basketball. Cells in the lining produce acid and other products to start the initial breaking down of their food. Feed material then passes into the small intestine. There are three parts of the small intestine: the duodenum, the jejunum, and the ileum. Food is further digested in the small intestine. A horse has over 70 feet of small intestine. Feed material then moves into the cecum. The cecum is equivalent to the human appendix, but where as our appendix has little necessary function, the equine cecum is very large and important. It is a big comma shaped organ that takes up most of the right side of the abdomen and is a place where bacteria start to break down the cellulose in plant material. Unlike us horses are able to obtain usable nutrition from plant material like grass and hay. This is because they have bacteria in their gastrointestinal tract that are able to break down cellulose. After the cecum, feed material moves into the large intestine. The large intestine in the horse is very large (hence the name) and actually contains four parts. It starts on the right side of the abdomen extends over to the left side, continues down the left side to the area near the pelvis at the back of the abdomen. It then makes a 180-degree-turn and returns to the front of the abdomen near the diaphragm. It then goes back over to the right side and along the right side of the abdomen. The large intestine is not attached to the body wall or any other portions of the GI tract for much of its length. It can weight up to 100lbs when filled with feed. It is another site of bacterial breakdown of plant material. Feed material then enters the short transverse colon before entering the small colon where it is formed into fecal balls before leaving through the rectum and out the back end of the horse.