Colic - part 1: Anatomy

It is ironic that I planned to dedicate today's post to colic and it turns out that my youngest son wakes us all by vomiting in the bed last night. The situation has now stabilised so that I can sit down at the computer for a while.

A difference being a human, compared to being a horse, is that we can get rid of disturbances in our digestion system at both ends but for the horse there is only one way out at the hind end.

To get all the facts in the right place, I have taken the help of Sara Beckman, farm agronomist. This will be a long posting, with lots of text and images. For the horse colic can turn into a life threatening condition and with that in mind this is given the place needed.

Colic is a generic term for painful conditions in the horse's belly. To understand why a horse may get colic, you need to know a little about what the horse's digestive system looks like and what happens in the digestive process.


(grovtarm=colon, tunntarm=small intestine, lever=liver, blindtarm=caecum)

The intestinal package fills the entire abdominal cavity behind the ribs on the horse and is separated from the chest cavity (where we find the heart and lungs) of by the diaphragm.


(magmun=orifice of the stomach, magsäck=stomach, mjälte=spleen)

The stomach of a horse is relatively small and can hardly be stretched. It is suitable for an animal that is constantly eating (12-16 hours per day). The muscle between the gullet (oesophagus) and stomach is very strong and the horse can not burp or vomit, everything they eat must pass through the intestine. The feed passes slowly from the stomach into the intestine as it is processed. If the horse eats too much of feeding that can swell, like oats or sugar beet pellets that has not been soaked enough, it can get cramp in the stomach. (colic due to over eating)


(tarmkäx=mesentery)

To avoid the intestines to move about in the abdomen, they are conected towards the spine by the mesentery. In horses mesentery is very long and loose and the small intestine can move about more than in many other animals. The small intestine is 16-24 feet long and absorbes easily soluble substances such as fat, simple carbohydrates, minerals and protein into the blood. If the feed contains toxins from harmful micro-organisms or substances too much gas can be produced with abnormal bowel movements as a result. If sand from contaminated feed or pasture is ingested it can stop the flow in the intestine and bowel movements are affected. (sand colic) In a horse with colic due to a stop, cramp or gas in the small intestines the gut literally "twist around itself", ileus, and if the blood supply is restricted the twisted part of the intestine dies fast - a very serious condition for the horse that can lead to death.



The horse's caecum (1 m) and colon (6-8 m) ads up to the largest volume in the abdomen (over 100 l). (Together they can fill half a bathtub.) Here, most of the degradation of forage is done with the help of microorganisms (bacteria, yeasts, fungi). The horse is completely dependent on their intestial flora to digest their feed - microbial waste products (proteins and fats) becomes food for the horse. Large amounts of gas is formed during the process that the horse has to let off.



The picture above shows the size of the colon. The horse can get colic from eating a diet rich in starch (long carbohydrate) with lot of concentrated feed, oats or barley and/or too little roughage. To much starch can lead to a growth of the gas-forming bacteria and to little roughage lessens the bowel movements. When the wrong micro-organisms grow you get a combination of improper intestinal flora with an increase in gas production and bad bowel movements that do not transport the gas quickly enough - the abdomen swells with great pain as a result. (gas colic or colon colic) A disturbed intestinal flora can also make the horse suffer from diarrhea. To restore the intestinal flora it may be necessary to give the horse freeze-dried lactic acid bacteria suitable for horses and/or live yeast.

A horse that eat enough of good quality roughage has good intestinal flora and bowel movements. If you place your ear close to the horses belly you should hear the rumbling sound of bowel movements and fermenting processes. The shape of the abdomen depends on the strenght of the abdominal muscles, the size and shape of the belly does not affect the horse's movements. A digestion that works fine is revealled by the look of the residual product's, solid ballshaped dung and a horse that is dry around the anus and under the tail.

A very common cause of colic is due to poor feed hygiene. Part 2 will focus on feed quality and hygiene.