Problems in the Equine Hindgut
Could your horse be suffering from colonic ulcers?
Could your horse be suffering fromcolonic ulcers?
You might have noticed that you’ve been hearing the phrase “hindgut health” in conversations about horses more so now than ever before. What does “hindgut health” mean in the context of your horse and what does it mean for you as his owner?
In this article, we break down the basics with help from experts Frank Andrews, DVM, LVMA equine committee professor and director of the Equine Health Studies Program at Louisiana State University in Baton Rouge, Louisiana, and Christina (“Cricket”) Russillo, DVM, a senior associate at Virginia Equine Imaging in The Plains, Virginia. Remember, in addition to the information provided in this article, always be sure to consult your veterinarian about what is best for your horse as an individual.
The horse’s hindgut—or large intestine, which includes the cecum and colon—is essential to the function of the horse’s overall digestive system and is important for bacterial content. When feed is processed in the horse’s digestive system, it is fermented and digested by bacteria in the hindgut. Fermentation is the chemical breakdown of substances by bacteria, yeast or other microorganisms.
Fermentation provides the horse with energy, vitamins, minerals and amino acids. When the horse suffers from poor hindgut health, he lacks these key dietary components. A lack of proper fermentation not only results in a decrease of these dietary essentials, but also in poor feed utilization, poor appetite, dehydration, poor coat and hoof condition, reduced immune function and a change in attitude. These negative effects will ultimately result in poor performance and training.
Horses are biologically designed to continuously consume small amounts of food, such as pasture grass throughout the day. However, the modern performance horse often has a lifestyle that vastly differs from this model of continuous grazing. When inherent habits like this are disrupted, compromised or totally eliminated and improperly substituted, then the horse is immediately at risk for digestive issues, Andrews says.
Problems in the Hindgut
Horses can experience a wide variety of hindgut health issues, ranging from diarrhea to torsion colics. However, according to Russillo, the most commonly occurring hindgut health issue in the performance horse is colonic ulcers, which are the focus of this article.
“Colonic ulcers are the number-one thing I deal with in my patient population,” she says. “Other issues that can pop up include infectious causes of diarrhea [such as Potomac horse fever], large bacterial shifts in the colon caused by orally administered antibiotics and dietary intolerances [for example, caused by changes in pasture]. But by and large, the thing that we’re day in, day out screening for in the performance horse is definitely going to be ‘could this horse have colonic ulcers?’” Russillo says.
What is a Hindgut Ulcer?
An ulcer can be defined as a thinning of the lining of the gastrointestinal tract. Ulcers can occur in the foregut (stomach) and are also referred to as gastric ulcers. However, ulcers can also occur in the hindgut, specifically in the colon, and are therefore referred to as colonic ulcers.
Andrews defines a hindgut ulcer as a depression of the lining of the colon. Hindgut ulcers are difficult to diagnose and often require an ultrasound. The severity of the condition is determined by the thickness of the colon’s outer wall.
Colonic ulcers are extremely difficult to truly diagnose because it is impossible to thoroughly examine the colon without surgery. “Surgical diagnosis of colon ulcers is the true gold standard, because the surgeon can either visualize the ulcer or perform a biopsy that can be examined microscopically to determine the degree of ulceration,” Russillo says. While surgery isn’t typically recommended to diagnose ulcers, it’s more indicative of just how hard it is to really understand to what degree a horse is affected, she explains. “Hence, we utilize the combination of clinical signs, ultrasound and blood work.”
Gastric ulcers have been a popular topic of discussion for years, but the conversation about colonic ulcers, on the other hand, has recently increased. Rus- sillo attributes this to a greater awareness that the problem exists in the first place. “Awareness and education are primarily why there’s been an increase in this discussion. We just now know that we need to look for it,” she says.
How Common Are Colonic Ulcers?
Ulcers are a common issue in performance horses. Russillo references a study performed in 2005 by Franklin L. Pellegrini, DVM, that examined the presence of colonic ulcers in horses at necropsy. What could be concluded, based on the study, according to Russillo, is that somewhere between 44 and 60 percent of horses have some level of colonic ulceration, with a higher percentage in performance horses. “Stomach ulcers are still more prevalent,” she says. “But hindgut ulcers are definitely a real thing and worth having conversations with owners about.”
Hindgut ulcers tend to have more profound clinical signs than gastric ulcers, according to Andrews. Signs include a recurring lack of appetite, lethargy, intermittent fever, colic bouts, occasional edema on the belly from a loss of protein in the blood, weight loss and thin body
condition. According to Russillo, typical signs include a combination of loose manure and large fecal balls or, in some cases, complete diarrhea. Liquid manure down the horse’s inner thighs and legs also serves as an indication.
When Andrews observes a horse with chronic issues of colic, diarrhea, lethargy or poor performance, he says people tend to think the horse is suffering from gastric ulcers. This is a common misconception. Typically, he says, these clinical signs actually relate to issues in the hindgut, which cannot be seen with an endoscope, so ultrasound examination and blood work are much more helpful. It should be noted that horses with colonic ulcers might have gastric ulcers as well due to stress, says Andrews.
In order to diagnose colonic ulcers, veterinarians most often perform a transabdominal ultrasound. This involves an ultrasound examination of the abdomen, with a focus on the horse’s right side in an effort to visualize the right dorsal colon. This, according to Russillo, requires specialized equipment and skill on the part of the veterinarian in knowing where to look. Typically, the ultrasound is positioned between the horse’s ribs and directed toward the colon. The veterinarian then attempts to measure the colon’s outer layer, or serosa. However, given the complexity in diagnosing colonic ulcers, even if the findings indicate colonic edema, clinical signs must be incorporated into the diagnosis as well, Russillo says.
Clues from Blood Work
Hindgut ulcers can also be detected through blood work, which provides information, in this case, on the horse’s protein levels. First, they will observe a complete blood count, looking for low protein concentrations in the blood. However, the total protein is typically within normal limits, so a specific albumin test should be done.
Typically, if a horse is suffering from hindgut ulcers, his albumin (the primary protein) concentration is low. Also, if there is inflammation in the hindgut, there will be a spike in the horse’s globulin concentration.
Veterinarians also observe a horse’s hemogram, a test measuring both white and red blood cell counts. A hemogram detects anemia and infection. Horses with colonic ulcers will be mildly anemic, which means they have a deficiency in red blood cells, or hemoglobin, in the blood and will have a high white blood cell count, which denotes infection.
According to Andrews, veterinarians are now utilizing a test that detects serum amyloid A (SAA) proteins. This test determines if the horse is suffering from inflammation. Andrews explained that hindgut ulcers or any ulcerative condition is associated with inflammation and the release of acute-phase inflammatory proteins like SAA, which the test is used to detect. A high value could indicate hindgut ulcers and follow-up testing may show if treatment is effective, which would be indicated by a decrease in the SAA value. The caveat to this kind of test is that an increase in SAA is nonspecific and any inflammation in the horse’s body can lead to an increase in SAA, meaning it is not a test that can differentiate stomach ulcers from hindgut ulcers on its own.
Treatment and Preventive Measures
In terms of treatment measures for the hindgut, Andrews starts by reducing the amount of bulk in the horse’s diet. He says hay is considered a “high-bulk diet,” as it takes up a lot of volume in the large colon, requiring the colon to work harder to mix it and digest it. It is also scratchy. Instead, Andrews recommends pelleted feeds because the volume of materials in the hindgut is much smaller and less scratchy. These products digest quicker and the residual content is therefore smaller.
The colon’s job is to pull liquid from the horse’s food and absorb the nutrients back into his system and then package the waste into manure. If a horse is diagnosed with colonic ulcers, then it is vital for the colon to be given time to rest. To do this, owners must reduce the horse’s intake of long-stem fiber, which means eliminating hay intake. Hay is a lot of work for the colon to digest and process and, in this case, it can scratch and cause irritation to the hindgut. Instead, hay should be substituted with soaked alfalfa cubes, alfalfa pellets, beet pulp or a complete feed that includes a horse’s necessary daily dose of fiber.
Decreasing a horse’s hay may cause concern for some owners, as hay is commonly fed to horses. However, Andrews
Horses are biologically designed to continuously consume small amounts of food, such as pasture grass, throughout the day.
Weight loss, thin body condition and lack of appetite are some of the clinical signs of colonic ulcers.
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