The alimentary canal in horses is basically the complete digestive tract from the mouth all way through to the anus. There are several different components or sections of the horse's alimentary canal, all which must function together to allow the food to be properly digested, nutrients to be absorbed into the bloodstream, as well as waste material to be eliminated from the body. Any one of the sections or components of the alimentary canal or digestive tract that is not working correctly can have minor or major affects on the horse's overall health and nutrition levels, regardless of the type of feed provided.
The top section of the alimentary canal includes the mouth, teeth, and esophagus, all which work to pre-break the food, usually grass, hay or grains, into smaller sections so that the digestive processes can be completed in the stomach and intestines. Older horses and horses with tooth and dental problems often have trouble in chewing and breaking up food items, leading to greater problems with digestion further along the alimentary canal. Saliva is key in the top section of the digestive tract as this helps to moisten the food as well as start the digestion. It is estimated that the average horse produces 10 gallons of saliva in a 24 hour period, most of which is absorbed by food that is being chewed to start the digestive process.
The esophagus is the long muscular tube that carries the chewed food from the mouth to the stomach. In an adult horse the esophagus is approximately 50 to 60 inches in length and pushes the food along using muscular waves. When horses eat food that is dry or they don't produce enough saliva food can become lodged in the esophagus, resulting in a condition known as choke.
The stomach of the horse contains many different glands for secretion of digestive enzymes and acids. Just like people, horses can have imbalances in the secretions in the stomach resulting in digestive problems. Horse can also have problems with digestion when the feed is changed suddenly, if they drink excessive amounts of water while eating or when incorrect types of foods form the bulk of the diet.
At the exit of the stomach is the small intestine, which is up to 70 feet long in a mature horse. This area is important in absorption of nutrients as well as regulation of the blood chemistry. The pancreas is found in the area of the small intestine and is essential for absorption of fatty acids, sugars, vitamins and minerals. The small intestine may become blocked or twisted, resulting in life threatening conditions.
The large intestine contains several discrete sections, including the cecum, which is responsible for further digestion of highly fibrous material. The cecum can hold between 28 to 32 quarts of the liquid digested matter and has a high microbe population for further digestion. The cecum empties into the colon that is divided into two separate sections, each about 10 feet in length. The colon is responsible for reabsorbing water and moving the waste material out of the body. Impactions and twists in the colon are relatively common in horses and can be fatal if not corrected.
The anus is the exterior opening of the small colon, the last foot that is known as the rectum. It is normal for a healthy horse to expel approximately 30 to 50 pounds of fecal material per day and have at least 6 bowel movements per day. Typically tumors or cuts on the anus can lead to problems with infections and obstructions, but these are relatively rare.