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Understanding the connection between Dysbiosis, Metabolic Disorder/IR and Systematic Inflammation and how to treat the equine to restore health

Part 1

by Gabriele Sutton

If one considers they are what they eat, they will quickly understand the principal upon which this hypothesis is established, that an unhealthy ulcerated gut sets the stage for equine disease. As the “gut” or the digestive tract, literally serves as a door to the Equine’s body, it is of the utmost importance that that “door” remains selectively functional. If ever it becomes “stuck open” or dysbiotic, the gastrointestinal tract transforms into a highway for disease.

Dysbiosis, also known as a “Leaky Gut Syndrome”, is defined as a perforated hind gut, an excessively permeable intestine or a condition of erosion and ulceration of the gastrointestinal tract. Symbiosis is defined as the relationship between organisms in which one organism is in an intimate association with another. A pertinent example of a symbiotic relationship is the intestinal flora of a healthy species lives in harmony with its host. As such the bacteria of the intestine is often referred to as “friendly” and helps to maintain homeostasis and many “health promoting” activities including detoxification, vitamin production, and protection against pathogens. If this relationship is out of balance, the mere overgrowth of so-called “friendly” bacteria, dys-symbiosis or dysbiosis results and inevitably leads to holes in the gut. Dysbiosis, and subsequent increased permeability of the intestinal mucosa, in general can be caused by a myriad of causes including protozoan parasites, bacteria, yeast, excessive antibiotic or NSAID use, parasite infestation, maldigestion, stress, and an imbalanced and restricted diet. The most critical point to consider with dysbiosis is the extreme damage it causes the horse by permitting bacteria, pathogens, and toxins to escape the intestinal lining and enter the bloodstream. This can lead to detrimental responses to pathogens and toxins leaking into the blood stream: 1.) an Immune Function System Response, 2.) a Systemic Inflammatory System response, and 3.) an Insulin Resistance (which can be measured by endocrine systems tests). Simultaneously, all nutrient absorption is impaired leaving the horse malnourished, in an extreme state of imbalance, and vulnerable to disease.

Dysbiosis allows the increased migration of bacteria and toxins through the intestinal wall. There the immune system of the horse is activated and forms antibodies in response to the invading pathogens. The increase in antibodies leads to large numbers of antigen/antibody complexes that may result in varied allergic reactions or inflammation when the complexes are deposited in tissues. When substances are no longer filtered by the intestinal wall and simply flood the blood stream, for example in the case of sugars or fructans, the pH balance is lowered creating a very acidic environment and an inflammatory predisposition. Inflammation in the gut inhibits absorption of nutrients, exacerbates vitamin and mineral deficiencies, compromises normal detoxification pathways, and the IgA immunoglobulin of the gut lining can no longer ward off protozoa, bacteria, viruses and yeasts. Subclinical acidosis is thought to result from overconsumption of either high starch concentrates or pasture grasses rich in fructans. When large grain meals are fed to horses, it is often impossible for the stomach and small intestines to sufficiently digest and absorb the massive onslaught of starch. Hence, some starch moves into the hindgut without being sufficiently digested. As digestion of easily fermentable starch progresses in the hindgut, the production of volatile fatty acids and lactic acid increases causing a significant decrease in the pH. When the hindgut endures insults such as this several times a day it teeters on becoming overwhelmed with acid. Additionally, because lactic acid is a stronger acid then the VFA, it can cause serious damage to the intestinal mucosa. The shift in pH provides an unfavorable environment for some of the many microorganisms that inhabit the hindgut and aid in digestion, in particular the fiber-digesting bacteria. For optimal performance, these bacteria favor an environment with a pH of 6.5-7.0. When pH drops to below 6.0, fiber-digesting bacteria become less efficient and begin to die off.

Once dysbiosis occurs in the horse, this essentially opens the door to many diseases such as founder, laminitis, inflammatory diseases (arthritis, myositis) and metabolic disorders (insulin resistance). Dysbiosis also contributes to endotoxemia, inflammatory bowel disease, Chronic Obstructive Pulmonary Disease (Heaves), liver disease, and colic. “Most often these conditions manifest in the horse as colic, which is often recurrent and unrelated to management. Chronic weight loss and chronic diarrhea may also result from leaky gut syndrome.” Further it has a devastating effect on the liver as it is recruited to filter all the “contaminated” blood from the intestine.
Many of our horses have elevated blood insulin levels without concurrently raised or lowered blood glucose levels. Insulin Resistance (IR) is a relatively new recognized condition which is also called Equine Metabolic Syndrome (EMS) or Syndrome X. Insulin Resistance Syndrome is a group of symptoms related to insulin resistance or hyperinsulinemia and the resulting physiological effects. This syndrome is characterized by decreased ability to transport glucose into cells. Equine Cushing’s syndrome has some of the same characteristics as IR. While some of the specific symptoms are different, the general seriousness of the metabolic diseases is very similar.
To identify if a horse might have a metabolic problem you may start by evaluating the horses’ appearance. You may find that your horse has fatty deposits on the base of the tail or has a cresty, fatty neck. A long hair coat, low energy and recurring tendon and ligament injuries, abscesses and laminitis are often a good indication when suspecting metabolic disorder. Much of the research indicates that if a horse is overweight, he is more likely to be insulin resistant. Imposing a weight loss program through calorie restriction and exercise to bring these horses back to healthy bodyweight may all that is necessary to get insulin/glucose levels under control. Certain breeds like Andalusians, Paso Finos, Quarter Horses, Morgan’s and of course Pony breeds are also genetically predisposed to EMS. Equine Metabolic Syndrome may predispose a horse to obesity or vice versa. Excess fat tissues associated with obesity may trigger an inflammatory response. Inflammation may play a key role in the onset of laminitis. So what does Insulin Resistance have to do with EMS? Insulin is a hormone secreted by the pancreas. When a horse eats, soluble carbohydrates in the food are digested in the foregut and converted to glucose (sugars). The glucose then passes through the walls of the intestines into the bloodstream. This is when insulin is called into service. As soon as the pancreas detects the increase in blood sugar, it sends insulin to latch onto the body’s cells (most cells have insulin receptors). The as the blood sugar passes by, insulin uses its master key to unblock the cell door. The blood sugar then enters the cell where it can be used for energy or stored as glycogen. In horses, Insulin Resistance is when the normal amount of insulin secreted by the pancreas simply isn’t enough to unblock those cell doors. When the pancreas secretes even more insulin and the higher level of insulin still can’t open the cell doors, we say that the cells are insulin resistant.

EMS can be linked to a high starch- high sugar diets. It is important to note that many of the ‘low starch’ feeds currently advertised in the market contain up to, if not more than, 18% NSC. In regards to specific feeding recommendations for insulin resistant horses, it is certainly a multi-faceted condition as each horse is an individual. Feeds could contain no or very low amounts of grain and contain no molasses and should guarantee a NSC content of no more than 10-11%. A low NSC formulation and small meal size is recommended for horses with EMS. Monitoring the forage intake of these horses is extremely important. Testing the forage’s NSC when managing a horse with EMS is vital. Owners may need to consider soaking hay for 30min in warm water or 60min in cold water to decrease the NSC content. Access to fresh pasture needs to me reduced, scheduled to early morning hours or night time turn out. Depending on the pasture grass species, the point of growing season, property altitude and the overall health of the pasture (stocking rate, fertilization status, etc.) some horses cannot be allowed pasture at all, some must be restricted through the use of dry lots or grazing muzzle.

Many of the conditions affecting EMS horses are directly related to the way these horses metabolize carbohydrates. So it’s important to get a basic understanding of how carbohydrates are digested. So, when choosing the right feed for the EMS horse, one must understand the sources of feed energy first. There are three sources of energy for horses; carbohydrates, fats and protein.

Carbohydrates are an important source of energy for horses, but not all carbohydrates are the same. There are a dizzying number of descriptors for the different types: non-structural carbohydrates, structural or fibrous carbohydrates, non-fibrous carbohydrates, etc. Soluble Carbohydrates are simple sugars and starches that are digested in the foregut. These carbohydrates have an immediate impact on blood glucose and insulin levels. Sources may include: grains, molasses, milk products (dried whey), and byproducts such as rice bran. Fermentable digestible fiber, carbohydrates from fibrous plant cell walls and polysaccharides, such as fructans, are digested in the hindgut. These carbohydrates are digested through fermentation performed by billions of microorganisms (healthy bacteria and protozoa). These carbohydrates have little impact on blood glucose and insulin after a meal. These carbohydrate sources may include grass forage, legumes, and byproducts such as beet pulp, soy hulls and wheat middlings. Indigestible fiber, which is roughage that isn’t absorbed, sweeps through the digestive tract to keep it clean and running smoothly. Indigestible fiber comes from hay and plant hulls. Soluble carbohydrates such as starches (grains) and sugars provide immediate energy because they quickly convert to glucose in the small intestine. Glucose can be used immediately or stored in the muscles as glycogen (stored energy). Glucose and glycogen are the fuels needed for high-intensity, short-duration exercise. Obviously, soluble carbohydrates are a valuable resource for horses. Horses are designed to handle a low–to-moderate load of soluble carbohydrates. But a supersize helping at a meal can spell trouble for horses that have difficulty controlling blood sugar. Digestible/fermentable fibers are also carbohydrates, but are digested differently than starch and sugar and tend not to rapidly increase blood glucose and insulin levels. Digestible fibers are fermented by the microbes in the horse’s hindgut into volatile fatty acids, which are then absorbed. These fatty acids are the primary fuel supply for maintenance activities and can be a source of energy for less intense, longer duration activity. The exception to the rules is fructans. Fructans are actually linked to fructose (simple sugars) and cannot be digested in the foregut. Therefore, they are fermented and digested in the hindgut. Fructans are not considered fiber, even though they are fermented in the hindgut similar to fiber. Excessive intake of fructans, mostly from cool season grasses, can trigger excess gas production and increase the risk of colic and laminitis. Horses with a history of laminitis may be especially susceptible. Indigestible fiber, though not absorb or used as energy, is vitally important to a horse’s wellbeing as it helps maintain normal gut function, water balance and fecal consistency.

Fats (Fatty Acids) are excellent sources of energy for horses. Metabolized in the foregut, fats deliver a smooth supply of energy without generating spikes in glucose or insulin levels. Certain fats play a role in a healthy hair coat, immune function and recovery after exercise. Unlike high starch diets, adding fat to a horse’s diet dies not increase the risk of digestive disturbances, such as colic. Although fats are an important part of a horse’s diet, EMS horses need to beware. Fats contain more than twice the calories per pound than either carbohydrates or protein. Therefore, weight prone horses should avoid too many added fats.

Protein and Amino Acids is not an efficient energy source for horses, but it is essential for growth. Hair, muscle, skin, hooves and mare’s milk are made primarily from protein. Amino acids (the building blocks of protein) rebuild tissue damage resulting from exercise or just everyday living. Protein is digested primarily in the small intestine (foregut). Enzymes digest proteins into their constituent amino acids and the amino acids are absorbed into the blood stream.

From the nutritional quality of the feed ingredients, to timing of meals, to exercise, to overall horse management, EMS horses thrive on consistency. Fasting is usually bad for these horses. The fasting/feeding cycle of two meals a day, even if its hay only, results in elevated blood glucose levels following each meal. Instead, these horses respond best to a feeding routine that mimics natural grazing behavior. Nibbling on long stem forage and eating several smaller concentrated meals throughout the day helps to keep their glucose and insulin levels on an even keel. Reduce body fat to improve insulin sensitivity and decrease the risk of fat-triggered inflammation.

  • Restore and maintain gut health
  • Restrict calories, but do not starve the horse
  • Control soluble carbohydrate intake
  • Utilize alternative sources of energy, such as fat and fiber
  • Feed the correct ration with multiple servings throughout the day
  • Supplement the horse to complement his diet and to address his specific needs
  • Weigh the hay to ensure the amounts are adequate to support proper gut health without adding excessive calories
  • Have the hay tested and ensure that the feed contains no more than 11% NSC
  • Exercise as often as possible.
  • Take caution when turning out on pasture
  • Treat inflammation with remedies that do not disturb gut health