Horse Digestive System – An Introduction

The digestive tract starts at the mouth and ends at the anus. It is a tube that runs through the body and the contents within this tube are really outside the body – like the hole in the doughnut.

The lining of the digestive tract keeps out the things that are harmful and even deadly to the horse while allowing in the materials it needs to fuel the cells and maintain the various parts of the body.  Selective absorption is the difference between the lining of the gut and the skin which otherwise is the same.

The tube is filled with a combination of acid, enzymes and bacteria and all of these are essential for the digestion of food and the survival of the horse. Attached is the liver that is critical to so many functions of the horse and really deserve a separate chapter but it is primarily a part of the digestive tract. It produces bile for the digestion of fats but because a horse doesn’t consume fat as part of the diet there is no need to make a lot and store it in a gall bladder. In addition, horses eat not in meals but in a steady intake for a major portion of the day. Therefore all horses are born without a gall bladder.

The tract is a one way street with all food pushed in one direction using muscular contractions (peristalsis) moving from the throat (esophagus) to the anus. Each section is divided into sections with specific purposes with specific acids, enzymes and gut bacteria. If any of these materials are moved to a different location (change in pH, dysbiosis), produced in excess (increased acid production) or are restricted (lack of an enzyme) then the digestive process is compromised. Further, if the tube integrity becomes compromised, the unwanted contents will start to move across this membrane into the body (leaky gut syndrome).

Inflammation of the lining of the gut is a major concern with horses today. Many human researchers suggest that up to 90% of our immune system is located in the gut making the rest of the body weak against attacks from other invaders (viruses, bacteria). This high activity is because there is a lot of inflammation of the gut system as it receives raw materials it was not developed to handle. The result is a change in the normal materials in the gut especially the resident bacteria. This is called dysbiosis and this leads to the epidemic amount of horses with ulcers of the stomach, the small intestines and the colon.

To discuss the GI tract without discussing nutrition is pointless so there will be a lot of overlap here and in the nutrition section under the CARE of the horse. The most serious issue in the digestive tract is colic. This is a word that strikes fear in horse owners with so many having lost at least 1 horse to this disease. However I see many equally disturbing problems with the digestive tract including diarrhea or squirts, stomach and colon ulcers, misbehavior and many metabolic issues. I will look at as many GI tract issues as I can think of but you may hear a common cause – stop feeding things to the horse they were never supposed to eat: grain, grain byproducts, pointless minerals, vitamins and supplements. At best you are wasting money getting an uncooperative horse. At worst you are causing them to become ill and even die.