Supplement to Prevent Leaky Gut Syndrome in Horses

A horse traveling in a trailer, increasing risk of developing leaky gut syndrome
Stress-challenged horses (such as those that travel frequently in trailers) are more likely to develop leaky gut syndrome, but supplementation with Aspergillus oryzae might help prevent the condition. | Getty Images

Gastrointestinal hyperpermeability (aka leaky gut syndrome) can cause a variety of adverse systemic effects as a consequence of uptake of inflammatory substances and microbes from the gastrointestinal lumen into the systemic circulation. There are many potential triggers for the development of leaky gut syndrome, including stress, NSAIDs, gastric ulcer disease, high starch diets, and intense and/or long-duration exercise, especially when combined with trailer transport.

Aspergillus oryzae Supplementation

Researchers looked at using a prebiotic—Aspergillus oryzae—as a preventive supplement that could help minimize leaky gut, especially in competition horses that travel and exercise [McGilloway, M.; Manley, S.; Aho, A.; et al. Dietary Fermentation Product of Aspergillus Oryzae Prevents Increases in Gastrointestinal Permeability (‘Leaky Gut’) in Horses Undergoing Combined Transport and Exercise. Animals 2023, 13, 951]. Aspergillus oryzae is able to amplify the abundance of probiotic healthy microbes and fiber-degrading microbes. In addition, it has the potential to provide anti-inflammatory effects and protect against colitis. 

Study Controls

In the study with eight healthy mares, an oral permeability marker, iohexol, was used to track its appearance and disappearance in horses challenged by transport and exercise stress. Blood was also sampled for serum amyloid A (SAA) and lipopolysaccharide (LPS). Two groups were formed from the eight mares. The four mares in Group A received an unsupplemented control diet, and the four mares in Group B were supplemented with the A. oryzae prebiotic in a pelleted product top-dressed once a day. Each of those two groups were then divided; two horses went into a stress-challenged protocol, and two served as non-challenged sedentary controls. 

The study lasted 28 days. The horses were then “washed out” for 28 days and assigned to the opposite group from which they started, and the trial was repeated.

A stress challenge involved trailer transport for 60 minutes and exercise at walk and trot for 30 minutes in sand, with heart rates around 150 bpm, just at or above the anaerobic threshold. This model of stress is reproducible for eliciting gastrointestinal hyperpermeability. Blood samples were obtained just prior to iohexol administration via nasogastric tube (without sedation), immediately after trailering, immediately after exercise, and then 1, 2, 4 and 8 hours following exercise. Manure was also collected prior to loading on the trailer, at the end of the hour-long transport, and after exercise. The non-challenged controls also received iohexol in the same time frame as the challenged horses, and blood samples were obtained at similar time points.

Study Results

Results from the first day for the stress-challenged horses showed the systemic appearance of orally administered iohexol whereas none was seen in the unstressed controls that remained in their stalls. The study results are very encouraging: After 28 days of A. oryzae supplementation, all stress-induced gastrointestinal permeability was eradicated. The researchers proposed that the mechanism might involve modulation of the gastrointestinal microbiome. 

A. oryzae as Leaky Gut Syndrome Preventative

The study summarized: “This supplement may be a useful dietary ingredient for horses undergoing combined transport and exercise stress as a prevention for gastrointestinal hyperpermeability.”

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