The lack of rain over the Highveld has affected the quantity and quality of roughage for both grazing and stabled horses. One of the consequences is impaction colic.
Here, fibrous material packs together, blocking the intestinal tract and causing severe pain. Although the blockage can occur anywhere between the stomach and the rectum, undigested roughage causes obstructions mainly in the caecum and colon sections of the large intestine.
The signs of impaction colic are generally not as severe as an acute torsion or a gas colic, where horses thrash and roll, but the condition can be life-threatening.
The horse usually looks depressed and stops eating. It is often dehydrated and the faecal pellets passed tend to be small, hard and dry. The horse may go down and refuse to stand up, or paw the ground and look back at its abdomen.
The horse may go down and refuse to stand up, or paw the ground and look back at its abdomen. Its rectal temperature is lower than normal and the eye and mouth membranes can be a dark reddish colour. Respiration and heart rate tend to be rapid.
If the impaction is not cleared, the horse may go into toxic shock or the intestines can rupture. A vet can diagnose impaction by doing a rectal examination, and, if necessary, taking blood.
The first step is to control the pain. Then a naso-gastric tube is used to reduce the volume of fluid in the stomach and dose the horse with about 4ℓ of liquid paraffin to soften the impaction.
It is crucial to rehydrate the horse. This is usually done intravenously, or through the stomach tube. Up to 50ℓ of fluid may be given intravenously over three to four days to correct the electrolyte imbalance. This is why it is advised that horses with impaction colic be hospitalised and observed over a few days.
On the first day of hospitalisation, they are muzzled to stop them eating and packing more half-digested food onto the impaction. They are then fed soft food such as a bran mash containing probiotics, until the horse starts passing faeces normally. Dry hay must be removed and horses hand-grazed on soft green grass.
Sometimes the impaction cannot be cleared by conservative treatment and surgery is indicated.
The most important cause of impaction colic remains poor quality, indigestible roughage. Make sure that you supplement with lucerne (at least 1kg to 2kg/day/horse) under drought conditions.
In hot weather, a horse needs to drink regularly; water deprivation for as little as four to six hours can contribute to impaction. Problems with the teeth such as sharp molar surfaces can also play a part, particularly with dry stalky Eragrostis hay or veld grass, as the horse cannot chew these properly.
Sudden changes of diet can also result in impaction colic, as the intestinal flora may not be able to digest the different ration. Change over to new feeds slowly and provide a probiotic feed supplement to assist digestion.
Dr Mac is an academic, a practising equine veterinarian and a stud owner.