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EQUINE HEALTH
LEAKY GUT SYNDROME IN HORSES
by Heather Smith Thomas
The horse’s gastro-intestinal tract is
an amazing organ. It performs many functions which include processing and absorbing all the nutrients that feed 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 inter- nal environment—keeping the “good” stuff inside and the “bad bugs” out.
Dr. Michael Lindinger, President of the Nutraceutical Alliance, and former profes- sor at the University of Guelph, has been involved in animal health research for a
long time, looking at problems like leaky gut syndrome, and is currently working on nutraceutical product development. “Leaky gut is 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 that 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 that is held together very tightly by tight junctions between the cells and other protein elements,” Lindinger says. 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 inflammation and immune responses, and be picked up by the blood- stream where they can act on many tissues. “This is why we feel very sick and experi- ence 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 will 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 cells. These toxins also cause inflammation of the intestinal wall and increased permeability, and then 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 pe- riod 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 syn- drome is often the result of two or more stress- ors acting together, according to Lindinger. For example, performance horses in training consume high starch diets (which can disrupt the normal digestive process) and experience
Mucus barrier
IECs (intestinal epithelium cells)
Nutrients from blood supply
Lumen of intestine
No passage of large molecules through intestinal barrier
Blood
Large molecules pass through leaky barrier from blood to lumen, and lumen to blood
The horse’s gastro-intestinal tract performs many functions which include processing and absorbing all the nutrients that feed the body, as well as playing a huge role in the body’s immune system.
Leaky gut is when 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.
56 SPEEDHORSE May 2020