E Q U I N E AT H L E T E
Belly buster Leaky Gut Syndrome in Horses By Heather Smith Thomas
The horse’s gastro-intestinal tract is a complex and amazing organ. It performs many functions which include processing and absorbing all the fluids and nutrients that feed and sustain the body, as well as playing a huge role in the body’s immune system. One of the most important functions of the GI tract is to act as a barrier between the external and internal environment—keeping the “good” stuff inside the body and the “bad bugs” out. Even though feed and water ingested by the horse may contain harmful pathogens, the barrier provided by the GI tract is usually sufficient. Dr. Michael Lindinger, president of the Nutraceutical Alliance (since 2012), and former professor at the University of Guelph for 25 years, has been involved in animal health research for a long time, looking at problems like leaky gut syndrome. He is currently working on nutraceutical product development. “Leaky gut is merely a syndrome, which means there can be a lot of different causes that can contribute to making the gut leaky,” he explains. “To put this in a human context, when we look at Crohn’s disease or irritable bowel syndrome or even just acute or chronic diarrhea, these are all examples of leaky gut syndrome. This just means the intestinal wall becomes leaky; fluids are not adequately absorbed into the body from the intestine, and fluids from the body can leak into the intestine—and toxins within the intestine can enter the body and cause many problems. Those leaks can be ulcers (such as gastric ulcers in the stomach, or duodenal ulcers, or colonic ulcers) but often if it’s something like diarrhea or irritable bowel syndrome, it’s actually due to a spreading apart of the cells that make up the intestinal walls,” he says. The intestinal wall is a very thin, single-cell layer held together very tightly by tight junctions between the cells and other protein elements. The wall is thin because this makes it easier for the body to absorb fluid and nutrients; they only have to pass through that one-cell layer, being transported through and between the cells by very specialized systems. When that thin wall becomes leaky, pathogens can go from the gut into the body, cause local 20 POLO P L A Y E R S E D I T I O N
inflammation and immune responses, and be picked up by the bloodstream where they can act on many tissues. “This is why we humans feel very sick and experience a very bad immune response when that happens. A horse is eating from the natural environment (uncooked food, unlike what we humans are eating) and always exposed to pathogens. These are usually contained within the gut however and don’t get into the body. The healthy gut has mechanisms for detoxifying most of the pathogens. The stomach, for instance, is very acidic and this kills many pathogens,” says Lindinger. There are also beneficial microbes in the intestine that attack and kill many of the pathogenic bacteria, viruses and fungi that are taken in with the feed. “A healthy GI tract helps maintain the gut in a non-leaky state and also helps fight off the pathogens that are taken in on a regular basis,” he says. Pathogenic bacteria and yeast may proliferate within the GI tract under certain conditions, however, and produce toxins that can damage the cells, compromising the tight junctions between those cells. These toxins also cause inflammation of the intestinal wall and increased permeability, and then they can leak through the wall. “Stress and poor water quality are probably the two biggest factors that can produce ulcers and leaky gut syndrome,” he says. Abrupt changes in diet, especially sudden increases in grain or fat, can also negatively disrupt the GI tract microbiome (the normal population of beneficial microbes). Changes in diet should always be gradual over a period of at least a week. Stress can compromise the gut There are a number of stressors that can damage the GI tract barrier. Leaky gut syndrome is often the result of two or more stressors acting together, according to Lindinger. For example, performance horses in training and competing in strenuous athletic careers, like polo, consume high starch diets (which can disrupt the normal digestive process) and also experience stresses of rigorous exercise, training and handling. This, compounded with the stress of stall confinement—a very unnatural environment for
