We often hear about gastric ulcers in horses, but hindgut ulcers are an equally serious problem that can affect the horse’s digestive system. However, because of their location–which can’t be reached with a scope–this type of ulcer is less commonly diagnosed.
Also known as colonic ulcers in horses or Right Dorsal Colitis (RDC), these lesions most often develop in the horse’s colon though they can also occur in the cecum. Though they don’t appear to be as common as gastric, or stomach ulcers, research indicates that anywhere from 44-63% of horses may be affected by hindgut ulcers.
A horse can also have both gastric and hindgut ulcers at the same time.
What Are Equine Hindgut Ulcers?
Hindgut ulcers occur when the epithelial cells of the intestinal lining become eroded for some reason. An open sore or ulceration forms, along with inflammation and thickening of the intestinal mucosa.
A decrease in the pH level of the colon caused by excess amounts of lactic acid is often associated with hindgut ulcers. This, in turn, may induce changes in the gut microbiome of the horse, allowing the “bad bacteria” to multiply while decreasing beneficial bacteria that help the horse to digest food.
Understanding the Horse’s Hindgut
The horse’s digestive system is made up of multiple organs, beginning with the mouth and continuing all the way to the rectum. The gastrointestinal tract, however, can be divided into two distinct sections: the foregut, which consists of the stomach and small intestine, and the hindgut, which is made up of the cecum and colon.
The foregut produces enzymes that begin the process of breaking down feed that a horse consumes, but the hindgut bears the responsibility of fermentation and turning structural carbohydrates from fiber into energy.
Fiber from forage makes up the majority of the horse’s diet and must be broken down by the microbes in the cecum and colon. In fact, feed may remain in the cecum for upwards of 36 hours, ensuring that microbes have enough time to digest feed material and produce energy needed by the horse. Volatile fatty acids and B vitamins are the result of this fermentation process which are then reabsorbed in the cecum.
As Dr. Amanda Bradbery, FullBucket’s Equine Nutritionist reminds us, “Amino acids cannot be absorbed by the cecum or colon. They’re too big. Volatile fatty acids can be absorbed because they are only 2, 3 or 4 carbons in size.”
From there, microbial fermentation continues into the large colon which is designed to efficiently process large volumes of fiber. The large colon also absorbs water, electrolytes and volatile fatty acids which are the main energy source for horses.
After that, feed material moves into the small colon which removes any excess water and returns it to the body. Material that is non-digestible is formed into fecal balls that are passed into the rectum.
Because of this highly important and complicated process which occurs in the cecum and colon, horses are known as hindgut fermenters.
When there is a disturbance in the balance of the microbiome in this region, the horse isn’t able to digest feed as well in order to absorb the needed nutrients. In short, Hindgut ulcers can interfere with the overall process of fermenting feed and absorbing water, which ultimately will negatively affect a horse’s health and well-being.
What Causes Hindgut Ulcers in Horses?
Gastric ulcers and hindgut ulcers share some common associations, which can sometimes make it difficult to diagnose and differentiate.
Whereas gastric ulcers are often associated with management practices such as routine stalling, forcing a horse to go for long periods of time without forage, as well as stress, hindgut ulcers are commonly associated with:
1) High grain, low forage diets. If a horse eats too much grain in a short period of time, lactic acid will build up causing pH to drop, killing beneficial bacteria in the gut. This is called hindgut acidosis.
Though the starch in grain is broken down and digested by enzymes in the foregut, when large amounts of grain are fed at once, not all of the starch will be digested by the small intestine and will instead move into the hindgut. This increases acidity and changes the microbial population in the hindgut, putting the horse at risk for developing ulcers in that area of the digestive system.
Dr. Bradbery explains, “Added grain is often necessary for performance horses to meet energy demands for exercise. More vigilant management is required for these horses to prevent the development of gastrointestinal ulcers.
Feeding hay before and with grain meals can aid in buffering the acidic environment of the foregut while supporting the microbial populations protecting the hindgut. Similarly, smaller and more frequent grain meals will promote foregut digestion of starches and sugars to prevent their fermentation in the hindgut to protect against microbial changes and pH shifts that result in ulceration.”
2) The overuse of non-steroidal anti-inflammatory (NSAID) drugs such as Bute and Banamine. Other NSAIDs that have been linked with hindgut ulcers include Ketoprofen, Firocoxib, and Meloxicam.
NSAIDs work by blocking two specific enzymes known as COX-1 and COX-2 in the horse.
Both COX enzymes produce prostaglandins, substances that can cause inflammation in the body. However, COX-1 produces certain prostaglandins that help protect the GI lining, while COX-2 produces prostaglandins that can be damaging in excess.
COX-2 inhibitors (Firocoxib, Ketoprofen, Meloxicam) only block COX-2 enzymes, which reduce inflammation and pain while sparing COX-1.
“This is why COX-2 specific inhibitors are prescribed for long-term use as opposed to your general NSAIDs (bute and banamine). By blocking only COX-2 (firocoxib, ketoprofen, meloxicam), we reduce pain and inflammation while still protecting the gut lining.
Non-specific NSAIDs (bute and banamine) that also block COX-1 will similarly reduce pain and inflammation, but put the gut lining at risk of damage, especially if the NSAID is given longer than 5-7 consecutive days.
Likewise, giving your horse more than the recommended dose of an NSAID may put your horse at risk for developing hindgut ulcers. Because of this, NSAIDs should only be given as directed and in accordance with your veterinarian’s recommendations,” says Dr. Bradbery.
3) Recurring stress. When a horse experiences stress on a regular basis, this causes the adrenal glands to produce high amounts of cortisol. When cortisol levels remain high, this inhibits synthesis of prostaglandins which help to produce mucus which is necessary to protect the digestive system from stomach acid. Performance horses may experience chronic stress from overtraining, frequent transport, and/or routine stalling.
Dr. Bradbery explains, “Horses under very intense training programs and performance events can often be deficient in long-stem forage because of their extreme energy requirements. But long-stem forage is key to gastrointestinal health in horses. It reduces stress, reduces boredom, protects the vulnerable tissues in the stomach, promotes a healthy hindgut microbiome, and provides the foundation of nutrients. As such, these horses are at highest risk of gastrointestinal ulcers.”
4) Parasites. These can attach to the intestinal wall or become encysted in the intestinal lining. When these parasites emerge (often in spring), this can cause inflammation and lesions in the hindgut.
Symptoms of Hindgut Ulcers in Horses
Hindgut ulcer symptoms in horses can be vague, especially in the beginning stages and they are also the same symptoms that often appear with gastric ulcers. They may include:
- Recurring episodes of colic;
- Poor appetite;
- Sudden girthiness;
- Dull hair coat; and
However, as the condition progresses, owners may see the following symptoms:
- Complete loss of appetite;
- Fever; and
Horses left untreated may develop dehydration, ventral edema (swelling under the belly and legs), and weight loss. Therefore it is important to have your horse assessed by your veterinarian if you suspect hindgut ulcers at all.
How Hindgut Ulcers are Diagnosed
As noted earlier, due to their location, hindgut ulcers aren’t nearly as easy to diagnose as gastric ulcers. Gastroscopy cannot be used, as with gastric ulcers.
Instead, veterinarians often rely on symptoms to make a diagnosis. Fecal occult blood tests are sometimes used, but they aren’t foolproof. Transabdominal ultrasound is the only definitive method of diagnosing hindgut ulcers; however this type of ultrasound requires specialized equipment and skill on the part of the veterinarian.
Best Treatment For Hindgut Ulcers in Horses
If hindgut ulcers are diagnosed or suspected, dietary and management changes are likely needed in order to begin the healing process. These changes may include:
- Discontinuation of NSAIDs;
- Adding long-stem alfalfa hay to the diet to provide buffering capacity;
- Feeding frequent small grain meals as opposed to one or two large grain meals;
- Making changes to your deworming program if parasites are the suspected cause of hindgut ulcers; and
- Supplementing with a high-quality equine probiotic product such as Fullbucket’s Extra Strength EQ Probiotic Pellets. The goal of this product is to restore beneficial bacteria in the gut and support the digestive system.
Management changes that reduce stress are also important for horses diagnosed with hindgut ulcers. Minimize stall confinement, strenuous training or exercise, and travel and maximize turnout time with other horses and allow grazing in small increments.
Like gastric ulcers, hindgut ulcers tend to be a management problem, but the good news is that, through dietary and management changes, both types of ulcers can be treated and the horse’s gut health can often be restored.
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