The simplest definition of colic in the horse is abdominal pain. The horse has a single, comparatively small stomach (monogastric), small intestine that is comparatively long, where most digestion takes place and a hindgut (caecum) where fibre and insoluble starch are digested.
This arrangement of the horse's digestive system together with the type of management regime that many modern horses are subjected to result in the fact that many horses may suffer several bouts of colic during the course of their lives. Very minor colics often go unnoticed
There are many instigating factors involved in colics and these may include irregular meals, the wrong type of feed or diet, inadequate time allowed for digestion prior to work or exercise, inappropriate watering, stress and tension, worm infestation and damage to the gut.
There are a number of different types of colic that the horse is susceptible to. These are:
1. Biliary colic caused by growths or parasites that block the bile duct.
2. Renal colic due to enteroliths or caculi in the kidneys or ureters.
3. Alimentary colic, the most common disturbance that is the result of gastro-intestinal tympany (gas retention), impaction and obstruction, spasmotic colic and intestinal catastrophy (twists, rotations and intussusception).
Management and diet play an important role.
Spasmotic colic: Amongst other reasons is caused by spasm of the intestinal wall due to migrating worm larvae. Feeding too soon after exercise and drinking cold water either too soon after exercise or in very cold weather are other factors.
Impactive colic: This type of colic occurs most frequently at the pelvic flexure of the large colon or where the small intestine enters the large intestine, and is the result of impacted food. It is caused by the ingestion of poorly digested forage e.g. straw, and may affect horses that tend to eat their bedding, older horses, and those whose teeth need attention.
Grass sickness may result in an impactive colic. This disease affects horses and ponies at grass and is associated with cold dry conditions and is therefor most likely to occur in geographic regions that experience these weather conditions. It is not known what causes the condition, though its considered that it is most likely that a fungus is implicated. Affected horses are constipated, usually as a result of an impacted colon and the most usual presenting feature for the owner of the horse are signs of colic.
Most horses that contract the disease die or are humanely destroyed dependent upon the form the disease takes i.e. acute, subacute or chronic.
Stomach rupture may be a sequel to impactive colic. Horses that have been reacting violently to abdominal pain, become quiet, go into shock and death follows shortly.
Sand colic is also an impactive colic due to an accumulation of sand in the caecum.
Tympany this is a gaseous accumulation in the stomach, caecum or colon. Gaseous distension can occur in front of an impaction or when the flow of digesta is prevented due to a twist or torsion of the intestines. It may also occur when food ferments within the stomach and intestines after too much grain has been ingested. As cereals contain high levels of digestible sugars, the rapid lowering of pH within the gut results in fermentation and the production of gas.
Intestinal catastrophy / twisted gut: This is a twisting of the intestine, a rotation of the intestine around its mesentery or a length of intestine telescoped into another length of intestine (intussusception). The blood flow is interrupted and gangrene may set in. Malignant tumours of the stomach are associated with abdominal discomfort. In older horses, lipomas (fat tumours) may twist round the intestine producing the clinical signs of a twisted gut. Stomach rupture can be a sequel to an intestinal twist. Horses that have been reacting violently to abdominal pain, become quiet, go into shock and death follows shortly.
Verminous colic: Is the result of damage by migrating redworm larvae causing blood clots in arteries supplying the small and large intestines that block the flow of blood to the gut
Diaphragm rupture: This may occur in brood mares following foaling or in horses that have been involved in major accidents.
Hernia: The most common sites for hernia are at the navel and the inguinal ring into the groin. A loop of small intestine or fat becomes entrapped through a natural or acquired hole in the abdominal wall and this cuts off the blood supply to the intestine resulting in colic.
Abdominal abscess: May occur in horses of all ages but usually seen in young foals.
The signs of colic indicate pain and discomfort that is the result of stretching and inflammation of the peritoneum that has many pain receptors and spasm of the muscle in the gut wall. The degree of the pain is dependent to an extent upon the cause. Typical signs include anxiety with the horse looking towards its flanks, a horse that lies down and gets up frequently, (the healthy horse gives itself a good shake when rising after lying down).
It may roll, and in the case of tympany and twists; violently.
It may also paw at the ground or kick out at its sides. It may be sweating and pass few droppings or in a spasmotic colic there may be diarrhoea. Intestinal movement sounds may or may not be heard. The horse may be inappetant; show increased temperature and pulse rates and may attempt to urinate.
Diagnosis is made on the symptoms that the horse exhibits and absent or increased gut sounds. Rectal examination can help to determine the type of colic.
Abscess: A prolonged course of antibiotics, but foals with abdominal abscesses often fail to thrive and die or are euthenased.
Hernia: Surgical intervention required. As soon as an abdominal or iguinal hernia is identified a vet should be consulted in order to take the necessary measures as soon as possible to minimise the discomfort to the animal.
Malignant tumours lipomas: Surgery, resection of the affected section of intestine can result in recovery. Early identification of the tumour has the best prognosis. Greys are known to be susceptible to tumours and vigilance on the part of the owner is essential. Avoid breeding mares that have tumours, as there is known to be an inheritance factor.
Diaphragm rupture usually requires exploratory surgery for a definitive diagnosis, but the prognosis is generally poor.
Spasmotic colic requires the use of a relaxant (spamolytic) drug. As this type of colic is usually due to worm infestation or an inappropriate feed and watering regime, adherence to a regular worming program and the correct feed regime can reduce the incidence.
Impactive colic: Large volumes of liquid paraffin, saline water and a gut stimulant via stomach tube are the most usual method of treatment. Passing a stomach tube can also relieve Grass Sickness that may result in impact colic. The inidence of this form of colic can be reduced by appropriate diet and management regimes, i.e. regular dental care, good quality forage should be fed and adequate time for digestion and exercise should be allocated. Avoid the horse ingesting sand either via drinking from water sources such as shallow rivers or streams with sandy bottoms or close grazing on sandy pasture that may result in colic.
The vet inserting a tube into the stomach to allow the release of gas relieves the pain of gaseous distension or tympany. In some situations a general anaesthetic is required in order to carry out a laparotomy (opening the abdomen) to relieve the gas filled intestines.
Ensure that horse that are fed high concentrate rations, also have an appropriate amount of roughage in their diets to reduce the incidence of gas build-up.
Intestinal catastrophy / twisted gut: If a horse suffering from a twisted gut is referred to an equine facility with the appropriate expertise and technologies then it may be saved. The prognosis is generally poor if pain does not respond to treatment, if the pulse rate is very fast and weakens, if the haemacrit rises above 50% and if the mucous membranes of the mouth and eye are purple or dark red.
In all types of colic, pain is relieved with analgesics, anti-spasmotic, anti inflammatory drugs and sedatives.
The horses' digestive system, its naturally excitable nature, together with modern management and feeding regimes makes the horse susceptible to colic. There are a number of herbs available that have beneficial effects on digestion and others that help to reduce stress and nervousness that may cause colic.
Sheep are known to ingest up to five pounds of sand per day. Horses who close graze sandy pastures will be at risk of colic and sand pasture should be avoided.
It used to be recommended that a horse showing the signs of colic be walked in-hand until the symptoms passed. If the horse rolled, it was prevented and restrained. It is now considered inappropriate to walk a horse that is in discomfort and it should only be restrained if its behaviour is so violent as to cause itself further injury. In some cases, rolling may actually effect a recovery.
Early veterinary supervision or intervention is essential.
Most of the colic cases admitted for surgery are due to high grain or concentrated diets, leading to rapid lowering of pH in the gut with death of specific gut flora and fauna and resulting endotoxaemia. It is a good idea for any horse owner to have a clear idea as to what they propose to do in the event of catastrophic colic in order that they can make a rational decision when under stress. Are the necessary surgical facilities available if required? Is the horse of particularly high sentimental or monitory value?
The horse person can minimise the likelihood of horses in their keep suffering from colic by having a thorough understanding of the horse's psychology together with its dietary and management needs. It is always useful to have background knowledge of the individual horse, as some will be more predisposed to colic than others.
If all the predisposing causes are taken into consideration then the necessary measures to prevent situations that may provoke colic can be reduced or avoided.