“Leaky Gut” Linked to Obesity in Horses

The detriments associated with obesity in horses are well described, yet the problem has reached epidemic proportions, according to researchers*. In addition to the classic concerns associated with excess body condition, a new issue has come to light: increased intestinal permeability, also known as “leaky gut.”

“Human research shows an association between obesity and increased permeability of the lining of the gastrointestinal tract,” says Kathleen Crandell, Ph.D., a Kentucky Equine Research nutritionist.

This increased permeability allows toxins and bacteria to pass from the inside of the gastrointestinal tract and across the wall of the intestine to the bloodstream.

“Once in circulation, those toxins and bacteria can cause inflammation. This can lead to systemic inflammatory response and disseminated sepsis—a widespread infiltration of bacteria throughout the body—not to mention the increased risk of developing laminitis,” Crandell explained.

As hindgut fermenters, horses have enormous amounts of bacteria in their intestinal tracts. While extremely helpful for fermentation of fiber to produce energy, if absorbed, these bacteria could cause extreme harm.

One theory to explain the link between obesity and leaky guts was provided by Kopper and colleagues. They postulated that fat tissue secretes pro-inflammatory molecules, such as tumor necrosis factor-α. This molecule stimulates other cells in the area to also secrete pro-inflammatory molecules. Together, those inflammatory mediators then disrupt the integrity of the intestinal wall, breaking down the tight junctions between individual intestinal cells that usually create a leak-proof wall, thereby allowing the abnormal passage of toxins and bacteria.

Veterinary researchers tested this theory in seven lean and seven obese horses and found that obese horses had increased permeability in some regions of the intestinal tract, specifically the jejenum, a portion of the small intestine.

“Owners are encouraged to familiarize themselves with what appropriate body condition looks like in horses and to routinely assess their horses to ensure they maintain an appropriate score (moderate) on the Henneke nine-point scale. Some barriers to achieving this goal include lack of familiarity with body scoring, the fact that some owners perceive a plumper horse as healthier, and because owners often enjoy feeding treats to their animals,” Crandell noted.

*Kopper, J.J., J.L. Travers, H.C. Schott, et al. 2019. Effect of body condition on intestinal permeability in horses. American Journal of Veterinary Research. 80(8):792-798.