The gut microbiome is intricately connected to many organ systems in mammals and has a large impact on the animal’s health. In a recent study, researchers at Nanyang Technological University in Singapore evaluated whether gut microbiota components such as butyrate-producing bacteria could impact equine athletic performance.
The researchers collected gut samples via feces from 58 Thoroughbred racehorses and 65 non-racehorses. Four breeds were represented among the non-racehorse controls. All 123 study horses had received no medications (antibiotics, anthelmintics, or NSAIDs) for two months prior to tissue sampling. Researchers extracted DNA from feces for metagenomic and metatranscriptome sequencing.
Research on Butyrate in Mice
The researchers conducted additional experiments on butyrate treatment in 30 eight-week-old mice. They split the mice into two equal groups and lavaged them with either sodium chloride (control) or butyrate (treatment) for 42 consecutive days. All received the same diet. On Day 42, the mice were fasted for six hours prior to running on a treadmill with an 11-degree incline until exhaustion. Researchers compared the athletic performance between butyrate-treated and control mice on the treadmill system for six weeks. The treated mice were able to exercise on the treadmill for a significantly longer time than the controls. The researchers collected feces following the exercises. Three days later, they assessed grip strength and found that the butyrate-treated mice’s grip strength exceeded that of the controls.
Next, the researchers analyzed exercise-related genes in mice skeletal muscles and small intestines. They euthanized the mice and processed their small intestines and skeletal hind leg muscles, randomly selecting three mice from each group for histologic analysis of muscle fibers and cross-sectional area, as well as mitochondrial DNA. The team found increased levels of 14 gene expressions of skeletal muscle differentiation in the butyrate-treated mice. Additionally, muscle fiber diameter and twitch fiber diversity were significantly higher in butyrate-treated mice, with increases in muscle mitochondria (the energy powerhouse of muscle cells that enhances skeletal muscle’s oxidative metabolic capacity). The authors reported that improved availability of adenosine triphosphate (ATP) enhances skeletal muscles’ explosive power and sprint activity for improved performance and strength.
Butyrate is typically associated with intestinal epithelial cell health and nutrition, with 95% of the butyrate produced by intestinal microbes going to support epithelial cells as an energy source. The researchers identified that the butyrate-treated mice had higher serum levels of butyrate than the non-treated mice. In the treated mice, butyrate passed through the bloodstream to act locally on skeletal muscle. The authors concluded that “microbially synthesized butyrate in the gut is a critical metabolite that may enhance host athletic performance.”
Butyrate in Racehorses and Non-Racehorses
For the horses, the team found statistical differences in the gut microbial communities between racehorses and the four breeds of non-racehorses. The racehorses had specific taxa that were associated with significant differences in gut microbiota function between the racehorse and non-racehorse groups, including metabolism of co-factors and vitamins.
“Out of all carbohydrate metabolic pathways, only the butanoate metabolism pathway was enriched in the racehorse gut, indicating a potentially critical role for butanoate in the gut,” the authors wrote.
Furthermore, at least one enzyme in all steps involved in the gut synthesis of butyrate in racehorses was significantly enriched compared to those in the non-racehorse breeds. In particular, butyrate kinase, a key enzyme for butyrate synthesis, was significantly more abundant in racehorses than in all four control breeds. The same was true for short-chain fatty acids in the feces.
Evaluation of a human athletic cohort yielded similar results: Professional athletes’ gut microbiota had a higher abundance of butyrate-producing bacteria compared to nonathletes.
Proposed Model for Microbe-Mediated Performance Enhancement
To meet the increased energy needs of exercise, the authors proposed a model for microbe-mediated enhancement of performance in which the butyrate produced by gut bacteria may enter circulation as an energy supply and target metabolism for an ergogenic benefit during athletic events:
- Butyrate in the circulation serves as an energy source for tissues and organs, like skeletal muscle.
- Butyrate might regulate skeletal muscle fiber type and remodeling.
- Butyrate increases the number and energy metabolism efficiency of mitochondria to provide skeletal muscles with energy during high-intensity exercise.
- The butyrate metabolic pathway increases available ATP for use in improving bacterial propagation to increase the abundance and colonization of butyrate-producing gut bacteria.
Take-Home Message
The authors determined that butyrate-producing bacteria and butyrate can contribute to athletic performance in mice, horses, and humans. This study suggests that pre-, pro-, and postbiotics using butyrate could be developed as therapeutics to optimize sports training and improve equine athletic performance.
Reference
Li C, LI X, Liu K, Xu J, et al. Multiomic analysis of different horse breeds reveals that gut microbial butyrate enhances racehorse athletic performance. NPJ Biofilms and Microbiomes May 2025; DOI: 10.1038/s41522-025-00730-w
Related Reading
- The Equine Gut Microbiome: A Hot Topic
- The Subtle Signs of Leaky Gut Syndrome in Horses
- Supplement to Prevent Leaky Gut Syndrome in Traveling Horses
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