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Jaak Van Overstraeten on colic: Causes, symptoms, risk factors and treatments

Tuesday, 20 December 2022
Gastric health

Photo © Nanna Nieminen for World of Showjumping.
“’Why?’ is always the question,” Jaak Van Overstraeten says about colic. “In general, 60% of chronic colic cases go undiagnosed." Photo © Nanna Nieminen for World of Showjumping.


Text © World of Showjumping



A horse stomach is a complex organ with different anatomic regions, and failures in its normal functions can have fatal consequences. Last year, World of Showjumping had a talk with equine veterinarian Jaak Van Overstraeten* to understand why a wide view is needed when looking at horses’ gastric health. This time, Jaak – who specializes in internal medicine – goes in detail about colic; from its definition to its causes, symptoms, risk factors as well as treatments. 

Collective term for abdominal pain

Colic is a collective term for all kinds of abdominal pains, which can be caused by various factors. “Intestinal problems are the main causes of a colic,” Jaak explains. “However, an issue like an ovarian tumour in mares can cause colic as well, and so can parasites – there are multiple causes and therefore a general examination by a vet as soon as possible after the first symptoms occur is always recommended. It is not easy for an owner to understand which type of colic their horse is suffering from, and even mild symptoms can be a sign of a very serious condition – and vice versa. Therefore, a vet should always be called to check on a horse with colic symptoms.” 

A vet should always be called to check on a horse with colic symptoms

A full diagnosis can be made in about 40% of all chronic colic cases, which means that the cause behind a colic will remain unknown in six out of 10 horses, Jaak points out. “’Why?’ is always the question,” he says. “In general, 60% of chronic colic cases go undiagnosed. Even with laparoscopy, you might not be able to find the cause and some diagnosis can only be made through surgery. In cases of colon torsions, I have had horses presented with severe abdominal pain and obvious colic signs, but I have also seen horses that just got depressed, stopped eating, got fever – and had a colon torsion. Some cases can be extremely difficult to diagnose at clinical exam, even with ultrasound, and sometimes horses are not getting the help they need in time.” 

A pumping system

Knowing the basic working mechanisms of the gastro intestinal tract is essential to understand what happens when a horse suffers from colic. “Proteins, fat/oil and sugar are absorbed in the small intestine and all the fibre that is left moves to the colon and the large intestine,” Jaak explains. “The large intestine is big, and therefore the passage is much slower, so the bacteria will have time to ferment the fibres and produce volatile fatty acids – the main energy source for a horse. When the passage time through the small intestine is too short – for example when a horse is stressed, or the amount of food is too big – the small intestine will not have time or capability to absorb all the sugar and too much of it will arrive in the colon, where bacteria will start to ferment it, causing gas formation and swelling.” 

The intestinal system of the horse is like a pump

“The intestinal system of the horse is like a pump; the small intestine in the beginning has a lot of fluid in it which is absorbed again in the colon,” Jaak continues. “It is a circulating system and even if a part of it is blocked – for whatever reason – the system keeps pumping. If the liquid can’t be absorbed anymore, the horse gets dehydrated and if the content of the small intestine cannot pass further, it goes back to the stomach. A horse’s stomach only has a certain volume and can rupture if overloaded; a normal volume of a horse’s stomach is around 20 litres and a horse weighing 500kg can produce 50 to 100 litres of fluid a day. The risk of a stomach rupture is one of the reasons we ask to walk the horse with colic symptoms and not let them roll until a vet arrives. A vet can use a nasogastric tube to decompress the stomach in case of a colic.” 

Colic symptoms

Symptoms of a colic can vary greatly and even the smallest signs of abnormal behaviour should not be overlooked, Jaak points out. “A horse sweating and rolling in its box with clear signs of pain is obviously a bad case of colic. However, there are mild symptoms as well and sometimes just a simple fever can be a sign of a very serious issue.” 

There are a few parameters that can be used to assess the severity of the symptoms and the easiest one is the pulse. “The pulse is a good parameter of the severity of a colic: When your horse gets dehydrated, the blood gets thicker, and the heart has to push harder to get the blood circulating. Also, the toxins produced by the bacteria can cause elevation of the pulse, and therefore a high pulse is always a reason for concern,” Jaak explains. “A normal pulse on a horse is around 24/minute. Most horses get a little bit excited when you examine them, but when you find a pulse of 80, you have reason to be very worried. You can feel the pulse of a horse on their cheek, under the cheekbone over the main artery. Normally a heart has four beats, where two of them fall together, creating a two-beat rhythm. However, a calm horse can even have a three-beat rhythm and it is easy to miscalculate the pulse. Therefore, it is good to ask your vet to explain how to correctly check the pulse of your horse.”

A horse sweating and rolling in its box with clear signs of pain is obviously a bad case of colic

“A second parameter to look for is the horse’s reaction to Buscopan. Usually, you should see an improvement in 15-20 minutes, and if the signs of pain return, you should immediately leave for a clinic,” Jaak says.  

In addition to the pulse and the reaction to Buscopan, the lumbar reflex is another good parameter. “When you push on the back, the horse should sink a little bit,” Jaak explains. “Not all horses do that though, but generally it is a sign of the abdominal pain not being too severe. When you have a colon torsion –  which is a really bad colic – the horse will stand totally stiff and not have any lumbar reaction. Horses’ gums can be used as an indicator as well: They should be pink and moist, not white, purple and dry. Lactate is another good parameter, but only for small intestinal colics, because colon displacements and torsions will have a normal lactate in the beginning. Lactate can be measured by a vet at home with a small portable device. Distended small intestinal loops at rectal or ultrasound exam are always a reason for a referral to a clinic. Hematocrit – the volume of red blood cells in the blood – is the last parameter to check.”


“There are two kinds of Buscopan,” Jaak tells about the medication used when treating colic. “We have the normal Buscopan Compositum which consists of two products; a painkiller and an intestinal relaxant. The other variant – which was only for human use before, but is now registered for horses as well – has no painkiller in it. It can be argued that the painkiller can mask some symptoms, but that is something I personally do not believe in. I always – always – give a small dose of both Finadyne and Buscopan and in my 24 years in practice I don’t believe to have missed colic symptoms because of these medications masking anything.” 

“However, when injecting Buscopan, you have to be extremely careful; it has to be given strictly intravenously,” Jaak points out. “One drop beside the vein can cause a huge inflammation and an abscess. Another issue is that the pulse is a very important parameter when assessing the severity of a colic, and Buscopan causes an enormous tachycardia. Therefore, the pulse is not a reliable parameter after a Buscopan injection. You have to keep in mind that every horse that has gotten Buscopan, will have a pulse of 80-100.” 

I always – always – give a small dose of both Finadyne and Buscopan

Flunixin is the active substance in Finadyne, whereas Buscopan is a market name for hyoscine butylbromide. “Finadyne is a stronger painkiller,” Jaak explains. “The advantage of Finadyne is that it captures the toxins which are produced by bacteria and are a huge problem in colic; the whole intestinal track from the stomach to the colon is colonized with bacteria and when an intestine is not working, the bacteria start to produce toxins which end up in the blood circulation of the horse, causing shock symptoms. These toxins can cause laminitis as well, which is a huge complication with colic.” 

“When horses are colicing badly, it can be difficult to inject them and this adds another risk,” Jaak continues. “There is only a thin layer of muscle before the principle artery of the head, and when your horse is not standing still, it is easy to miss the vein and accidentally hit the main artery – which in case of Buscopan could have fatal consequences if the active substance enters the brain.” 

Colic surgery and complications 

Surgery is sometimes the only option in helping a horse with a colic. “The quicker a surgery goes, normally the less complications there will be,” Jaak says. “In general, I think people are not aware of the risks of colic surgery and the survival rates. When we speak about survival rates, a colleague of mine followed up on his patients and only 40 % of horses that survived one surgery lived more than four years.” 

“In the end, intestines are not made to be touched by human hands and that is a huge problem with colic surgeries,” Jaak continues. “Horses that have had surgery often suffer from re-occurring colic, and in most cases the cause isn’t found. Even in human medicine, complications like ileus – the small intestine failing to work without any mechanical obstruction – are well-known post-surgery complications.” 

Intestines are not made to be touched by human hands and that is a huge problem with colic surgeries

Most of inguinal hernias – where a part of the intestine protrudes through the abdominal muscles – cause a small intestine colic and in principal always need surgery. “There is a possibility to manipulate the small intestine without surgery in inguinal hernias, but it is something you cannot do at home. When you have a small intestine colic with an obstruction, if you are quick enough, manipulation during surgery can be enough, but if the small intestine is blocked too long, the blood circulation of that part of the intestine will be damaged. When the damage is too big, you should take out the damaged part – and one can understand that the survival chances of those horses are much smaller; when you have to stich two parts of the intestine together, the risk for leakage is bigger, the duration of the surgery will be longer and therefore the complications can be more severe.”

“The normal recovery time after a colic surgery can vary from two to six months, depending on the healing of the abdominal wound,” Jaak tells. “The main problem is that the weight of the abdomen pushes on the scar and the abdominal wall, and the stable environment is never sterile; wound infections are common.”

Risk factors

Food is the main risk factor for colic – sugar and starch in particular. “When dietary regimes of horses which needed colic surgery were recorded, almost all of the cases that were operated were horses fed with grains or commercial mixes,” Jaak tells. “It is really rare that horses that are day and night in the field without any additional food arrive to the clinic for colic surgery. However, it is not always possible to feed horses without grains or commercial mixes, but one should avoid large amounts."

“Genetic problems, parasites and stomach ulcers as well as the age and sex of the horse are other risk factors,” Jaak continues. “In grey horses, melanoma can be a risk factor; internal melanomas can cause obstructions in the intestine. Stress is a risk factor as well as it can cause gastric ulceration, and secondly it can have an impact on the activity of the small intestine, causing the food to pass too quickly and arrive in the colon with too much sugar. Competing and traveling are certainly risk factors as well. However, there are many unknown factors that we cannot control.”

Horses are made to eat all day long, with a low energy content

While completely preventing colic is impossible, the horses’ diets play a huge part. “Horses are made to eat all day long, with a low energy content,” Jaak says. “Feeding grain twice a day means a high energy content which is the opposite of what horses are made for and what is natural for them. Feeding often and keeping an eye on the sugar content is important. However, a lot depends on your hay; sometimes hay can be very high in sugar as well. When you have hay with a low sugar content, starch will not be a problem, but when you have hay with a high content of sugar in combination with grain, it can become an issue. I would always recommend having the hay analysed but I know in reality it can be difficult; many times, you have hay from different fields and even in one field the quality can vary. A simple supplement like paraffin oil can easily be given for horses that are prone to producing gas in the colon; it will break the gas and helps avoid a gas colic.”

Another big risk factor is movement – or more precisely, the lack thereof. “It is really important that horses move enough,” Jaak says. “That also promotes the intestinal movement.” 

It is really important that horses move enough

“It is actually strange how little science is used when it comes to feeding horses,” Jaak points out. “Top teams in other sports, like in cycling for example, have nutritionists and they know their athlete’s ideal weight for optimal performance; weighing less means less power and weighing too much affects gravity. However, with jumping horses it seems no one knows what the horse’s ideal weight is. In general, we seem to feed like we think we should feed, instead of actually knowing why or even understanding the basic anatomy of the horse. We don’t need special solutions; we need clear and simple advice. General quality of the food is important and what is often overlooked, is that one should feed with a short turnover.” 

“We understand a lot and there are many studies done,” Jaak says about the current knowledge of the complex system that is a horse’s stomach. “However, the bacterial colonization of the intestine plays a huge role in a colic and that is something we don’t yet know much about. Even in human medicine they find that the stomach bacteria play a role in developing diseases like Alzheimer, so probably this will be a subject to focus on in the future.”


* Jaak Van Overstraeten graduated Magna Cum Laude from Ghent University in 2000. He first worked in general practise before founding his own private equine practise with special interest in internal medicine and reproduction. Jaak specializes in referral work from colleagues in the field of internal medicine.


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