Impaction Colic - what, why and how to avoid

Anna Harrison BScHons BVScHons CertWel MscIAWEL MRCVS and Honorary Vet to Donkey Breed Society, explains

- Anna Harrison

Colic is such a broad term - to most equine owners it means gut pain and this is quite correct. Just bear in mind that if a donkey has pain in organs not associated with the gut but still within the part of the body between the front and back legs (e.g., lungs, kidneys, bladder, uterus, spleen) this will still present as 'colic' pain.

We'll take a look at one of the common causes of abdominal pain - impaction colic.

First a quick anatomy and physiology lesson on the gut or alimentary tract to give it its technical term - all 21 metres of it! The cheek teeth have to be working as an efficient grinding unit, reducing long forage fibres to lengths of no more than 3mm. Balls of chewed food, moistened by the copious saliva produced, are propelled down the oesophagus (gullet) by regular muscle contractions known as peristalsis which occurs throughout the alimentary tract. On entering the stomach, which is only the size of a small rugby ball by the way, some protein digestion occurs but the bulk of forage moves through into the intestines undigested because it is made up of cellulose and the donkey itself has no digestive enzyme capable of breaking down cellulose (cellulase). In the small intestine proteins, fats and starch are digested and absorbed. Undigested cellulose ends up in the caecum and large colon where literally trillions of microbes exist which are capable of digesting cellulose and release energy in the form of fatty acids that the donkey can use. Water is resorbed towards the end of the tract and what is left is propelled into the rectum in balls which are expelled via the anus.