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Travel stress and Colitis in horses

We here at Combined Horse Transport (CHT) have dedicated almost 30 years of research and experience into continually improving the welfare of animals in transit.An area of particular interest to us has been that of travel stress or travel sickness / shipping disease as its commonly referred which encompass many different forms ranging from the more serious such as Pleuropneumonia and laminitis to other forms as mild as a slightly elevated temperature.
There is absolutely no doubt CHT has been a leader in this topic and most definitely have the best track record of the least cases which is a direct result of an important portion of our rigorous continuous improvement program of promoting awareness combined with implementation of effective corrective action (the development of our fleet of Mega Arks) and staff training, all sourced from our extensive experience.. Whilst these days it is extremely rare for us to encounter a horse effected by any of the above it is however, becoming more alarming the number of horses we see suffering from Colitis. Fortunately we discover or suspect many of these before they are loaded on to our transporters or at our transit stables after they have been delivered for us to collect.
Unlike travel stress where over the years we have been able to gather a lot of information and experience to make adjustments which has dramatically reduced the occurrence this is not quite the case with Colitis other than by education and awareness hence this news bulletin whereby some better managed husbandry procedures by owners may just possibly reduce some cases.
Basically in layman’s terms Colitis is an imbalance of the flora in an adult horses intestine which may have come about from many different causes such as sand (the most common we have noticed) parasites, poor quality drinking water, the use of particular antibiotics just to mention a few whereby the lower and larger part of the intestine referred to as the Colon is damaged and unable to perform its normal function of extracting fluid from the intestine resulting in severe diarrhea. Whilst this ailment may exist undetected and cause no problem to a horse in a relaxed environment the elevated stress levels provoked by travel may be enough to activate a case of colitis. As one vet put it to us a simple procedure of moving a horse from the back paddock to the front paddock can be enough to set this off.
Basically our message here is to advise or remind you, the horse owner, to ensure your horse is healthy before contemplating travel and take precautions such as:-
• Feed a staple of a good roughage source in the form of quality hay or pasture free of toxic weeds. Use grain as a supplement, not as a staple.
• Avoid sudden changes in diet.
• Insure access to fresh water at all times. Avoid relying on stagnant or contaminated ponds, streams, or ditches.
• Maintain an appropriate parasite control program.
• Insure he is free of sand in the stomach.
• Use antibiotics only when truly necessary and under the guidance of your veterinarian.
• Always communicate with your veterinarian immediately if you notice diarrhea in an adult horse, before the problem becomes severe.
Many interesting articles can be retrieved from the net by simply googleing “Colitis in horses”. For those interested in knowing more we have included one of these articles below as written by Doug Thal, DVM.

Intestinal Health & Colitis in Adult Horses

By Doug Thal, DVM

The equine digestive tract is a complex and fragile system which is easily disrupted. The intestines, which are a total of about 80 feet long in an average adult horse, digest and absorb feed, extract nutrients, absorb water, and eliminate waste. One sign that the intestines are disturbed or otherwise stressed is the development of diarrhea. The causes of equine diarrhea can range from mild to life threatening. In adult horses, these causes include everything from mild stress to fatal intestinal infection. Given that the function of the intestine in adult horses differs from that in foals, I will discuss foal intestinal disorders in a future article.

The Large Colon

Digesting, absorbing and utilizing the normally indigestible sugars in hay and other green plants would be impossible for horses without the action of microbes (bacteria and protozoa) in their specially adapted large colon. Microbes break down these sugars into products that can be readily absorbed and used by the animal. The large colon is the car tire- sized lower part of the intestine which contains a huge population of these microbes. It is critical to the digestion and absorption of nutrients and water uptake. These processes are interdependent and require a normally functioning flora (microbe population), and a healthy colon lining made up of cells which absorb water and nutrients, and functioning vessels to move fluid into the circulating blood.
Diarrhea is an excess of water in the manure and is caused when anything disrupts the very specific balance of microbes in the colon or damages the colon lining or circulation. When water is not absorbed in the colon, it is lost into the manure resulting in loose stool or diarrhea. Serious diarrhea accounts for huge water loss, and can cause rapid loss of fluid from the circulation. This leads to a vicious cycle of low blood pressure and reduced blood flow to vital organs (circulatory shock), which can quickly result in death if untreated. In contrast, mild diarrhea (soft manure) is usually not considered a problem
It is important to differentiate between acute (sudden) and chronic (long term) diarrhea. Mild, acute diarrhea may be caused by stressful situations such as trailering. This is a reflex caused by the nervous system. Most horses produce normal manure soon after the stress is resolved. Rapid diet change alters bacterial populations resulting in diarrhea and usually improves as the intestinal balance shifts back to normal. In severe cases, however, it can lead to colitis, a possibly severe inflammation of the colon which I will discuss.
Chronic diarrhea in adult horses usually relates to a damaged colon wall and reduced uptake of water. Horses with chronic parasite infestation, inflammation or tumors involving the colon wall often will have chronic diarrhea. These horses usually also have severe weight loss. Parasite infestation causes weight loss and can cause diarrhea by causing low-grade colitis through damaging the intestinal wall.


Colitis is inflammation of the colon. When the colon wall is irritated it loses function, thereby losing its ability to uptake water, and may actually dump fluid from the blood stream into the manure. Colitis can be caused by a variety of problems, but often results from a disruption of the normal bacterial flora due to a rapid feed change. A classic example of this is grain overload, which can cause entire populations of microbes to die off and others to flourish. This imbalance and direct damage to the colon from the acid products from the grain can lead to colitis, which results in diarrhea.
Bacterial colitis is caused by overgrowth of undesirable organisms in the colon. Overgrowth of organisms that normally live in the colon can take place, or a new organism may be introduced. Often we do not know why these bacterial populations shift, but when they do, life threatening colitis and diarrhea can result. Bacterial colitis is often caused by types of Salmonella and Clostridial organisms. Understanding where these organisms come from or what causes them to multiply suddenly has proven to be difficult and is still not completely understood. Researchers have learned that some types of bacteria can be transmitted through contact with horses that are shedding the organism in their manure. Some have been isolated from environmental sources like contaminated drinking water. An important point is that these organisms appear when the normal flora of the gut is disrupted, especially by the use of certain antibiotics.
The severe causes of acute colitis that I have discussed are rare but are more common under more crowded and stressful conditions. A critical factor in whether or not a horse becomes infected with these diseases is the immunity of that particular horse (related to its general health), and the healthy balance of microbes in the intestine. There have been serious outbreaks of bacterial colitis in equine hospitals and breeding farms. An important factor in these outbreaks is that most of the horses infected are sick or stressed and usually have been on antibiotics. Antibiotics alter the normal bacterial populations and make horses more susceptible to overgrowth of these bacteria. A more rare cause of colitis in the Southwest (more common in the Northeast) is Potomac Horse Fever, caused by an organism which relies on a parasite in freshwater snails for its life cycle and transmission to horses.

Sand Colic

Sand accumulation , so called “sand colic” also often causes diarrhea. Horses accumulate sand accidentally as they eat hay from the ground or graze short stubble in a sandy pasture. Diarrhea results from partial blockage of the colon, and irritation to the colon lining from large quantities of sand. At its worst it can involve accumulations of more than 100 lbs of sand. The critical factor determining a horse’s likelihood of getting sand impaction is whether or not the soil upon which horses are fed is sandy or not. Fine clay soils are not likely to accumulate in the colon as true sand is.

Treatment & Prevention

Veterinary diagnostics for horses with diarrhea of all kinds include a careful history and physical exam. Laboratory tests on blood and manure are used depending on the case. The veterinary treatment of diarrhea in horses depends on a properly diagnosed cause. Stress induced watery manure, for example, might require no treatment. Colitis, on the other hand, must be treated immediately and often requires hospitalization. Types of treatments in these cases may include oral and intravenous fluid therapy, plasma, antibiotics, anti-inflammatories, and careful nursing care. Unfortunately, severe colitis has a high rate of complications, including laminitis, which can also be life threatening.

Horse owners should observe the following precautions to reduce the likelihood of diarrhea and colitis in horses:
• Reduce stress and provide the most natural lifestyle possible, with consistent turnout,
• Feed a staple of a good roughage source in the form of quality hay or pasture free of toxic weeds. Use grain as a supplement, not as a staple.
• Avoid sudden changes in diet.
• Insure access to fresh water at all times. Avoid relying on stagnant or contaminated ponds, streams, or ditches.
• Maintain an appropriate parasite control program.
• Use antibiotics only when truly necessary and under the guidance of your veterinarian.
• Always communicate with your veterinarian immediately if you notice diarrhea in an adult horse, before the problem becomes severe.
• Horses suspected of having intestinal infection should always be isolated until your veterinarian can advise you.

Prevention of sand accumulation involves determination of whether or not your soil type puts your horses at risk. If your soil is sandy, you should take proactive steps to insure that your horses do not accumulate sand. These steps are:
• Feed off the ground in mangers or tubs. Insure that the spillage from these is not picked up from sand (lay down mats or other barrier under the tubs).
• Use psyllium as a preventative supplement as per the instructions of your veterinarian.
• Horses grazing on sandy pasture should not be allowed to graze down to short stubble. When they do this they are more likely to ingest sand.

Diarrhea is an uncommon but potentially serious symptom in adult horses which is a sign of disruption of intestinal function. The observation of diarrhea in an adult horse should not be grounds for panic, but should prompt you to monitor the situation carefully and contact your veterinarian right away.