Microbiota Differ Between High- and Low-Performing Horses

The health effects of the intestinal microbiome extend well beyond the horse’s hindgut. According to a new study, one positive effect may include enhanced performance.^* In the study, researchers found that the microbiota of high- and low-performing horses differed significantly.

 “Microbiota” and “microbiome” are often thought of as synonyms, yet there are differences between the two terms. Microbiota describes the living microorganisms found in a defined environment, such as hindgut microbiota. Microbiome refers to the collection of genomes from all the microorganisms in the environment, which includes the community of microorganisms as well as the microbial structural elements and metabolites. Defined in this way, microbiome involves greater scope than microbiota.^**

 A healthy intestinal microbiome positively affects digestive processes, metabolic functions, immune status, and other body processes, including the gut-brain axis.

“Many factors influence the microbiota’s diversity and richness, which reflects the type and amount of different bacterial species present. These include diet, stress, medications, and physical exercise,” explained Catherine Whitehouse, M.S., a Kentucky Equine Research nutrition advisor.

In addition, several elements influence a horse’s athleticism, such as genetics, training, fitness, conformation, and several other intangible factors. South Korean researchers recruited high- and low-performing Jeju (native South Korean breed) or Thoroughbred horses to evaluate the association between intestinal microbiome composition and racing performance. Horses were matched by age, body weight, diet, training, body condition score, soundness, vaccination, deworming, and medications. All horses were offered roughage and concentrate feeds totaling 2.5-3% body weight daily.

Fecal samples were collected from all horses and analyzed using standard 16S rRNA gene amplification techniques to measure diversity, richness, and bacterial composition.

Richness and diversity (i.e., the number of bacteria and their relative abundance) were higher in high-performing horses than in low-performing horses.

“Differences in specific types of bacteria were also noted. High-performing horses had a significantly greater abundance of fiber-fermenting bacteria than low-performing horses. Further, potentially pathogenic bacterial species were more abundant in low-performing horses,” shared Whitehouse.

According to this study, racing performance seems to be associated with the composition of the intestinal microbiome. However, the study does not reveal if the microbiome is healthier in high-performing animals or if exercise positively affects the microbiome as reported in humans. Further study is certainly warranted.

Certain feed management strategies will help bolster the health of the hindgut, Whitehouse said.

“It’s important to supply optimal amounts of quality forage, as highly digestible forages can help reduce reliance on concentrate feeds. Consider dividing large amounts of concentrate feed into three or four smaller meals throughout the day and minimizing the time a horse spends without access to feed. Performance horses may also benefit from receiving a hindgut buffer to help offset the stressors of training and competition and help support a stable microbial population,” she suggested.

 ^*Park, T., J. Yoon, Y. Yun, and T. Unno. 2024. Comparison of the fecal microbiota with high- and low-performance race horses. Journal of Animal Science and Technology 66(2):425-437.

 ^**Berg, G. et al. 2020. Microbiome definition revisited: Old concepts and new challenges. Microbiome 8:103.