Friends, Freedom and Forage: Scientifically Proven Ways to Prevent Equine Gut Disorders

June 19, 2024

By Sarah Griffiths, DCH

For the past several years, I have been immersed in the science of why so many horses are suffering from gastrointestinal diseases like ulcers and colic. Paired with my personal and clinical work with horses, I’ve made some discoveries that I can’t unsee. Recently, I was fortunate enough to be part of an equine gut dissection and this lead me even further down the rabbit hole of why and how to help horses in this area. Some of my realizations have caused me to prioritize my own horses’ needs in a whole new light. It’s taken some humility to do this!

Equine Gut Disease Stats:

According to the National Institute of Health, the state of equine gut health is in crisis…

  • 70-90% of pleasure and performance horses has gastric ulcer syndrome
  • Colic remains the number 1 cause of death in domestic horses
  • The primary lesion for recurrent colic in horses is gastric ulcer syndrome

As I’ve stated before, these numbers are crippling. We can’t ignore them and keep doing what we’ve been doing. We need to make changes. Gut health is crucial for a horses’ well-being, mentally and physically. It may sound dramatic but choosing not to make changes to enhance your horse’s GI health could be life-threatening.

The equine gut is an evolutionary marvel (over 200 million years old) with a massive fermentation capacity compared to most other species on earth. It is a huge part of why horses look and behave in the way that they do. It is the central hub for which health can be either promoted or hindered. Microbiology research has exploded in terms of studying the gut in both humans and animals for this very reason. Richness and diversity in bacteria, fungi and virus in the gut is linked to the highest state of biological resiliency.

Our modern version of how to create gut health is horses is severely lacking. Promoting a healthy gut takes more than giving minimal food sources, supplements and a small space to live in. It takes more than spending 1-2 hours per day with your horse and then putting them back into a sterile and lonely setting. It takes a hard look at why each one of us chooses to have horses in our lives and how to see them through a lens based on equine-specific needs instead of our own.

Recent research highlights the importance of a diverse, species-specific diet and environment for promoting a healthy gut and overall well-being. Below, you’ll find the undeniable scientific connections between a horse’s diet, its living environment, and gut health, underscoring their proven equine-specific needs for diverse plant intake, soil exposure, and social interactions (eg. friends, freedom and forage). We’ll also explore the limitations posed by a sterilized living and social environment, and ultra-processed diets.

The Importance of Species-Specific Diet and Environment

a) Diverse Plant Intake and Gut Microbiome

Horses are hind gut fermenters, designed to graze on a variety of plants. Plant diversity supports a rich and diverse gut microbiome. In the ancestral equine diet, wild horses will eat a range of over 40 plant species including grasses, shrubs, trees and herbs. They will also eat different parts of the same plants during different seasons (eg. leaves, flowers, tree bark and plant roots). This allows them access to more than any pre/probiotic supplement could ever offer. Pre/probiotic supplements are far from equivalent to immersion into a living ecosystem with thousand, if not, millions of beneficial microbial strains and hundreds of potential prebiotic fibre sources. A diverse gut microbiome is essential for effective digestion, nutrient absorption, and immune function. Studies have shown that horses grazing in living ecosystems have a richer and more diverse gut microbial population compared to those on monoculture diets.

For example, a study by Dougal et al. (2013) found that horses grazing on a variety of plant species exhibited greater microbial diversity in their gut compared to horses fed a limited diet. This diversity is linked to improved digestion and a lower incidence of gastrointestinal disorders.

b) Soil Intake and Microbial Health

In addition to diverse plant intake, living soil consumption plays a significant role in equine gut health. Soil contains a myriad of microorganisms that can colonize the gut and enhance microbial diversity. Horses naturally ingest soil while grazing, which introduces beneficial microbes and helps maintain a balanced gut ecosystem.

A study by Schwarm et al. (2015) highlighted that horses with access to soil exhibited higher microbial diversity and stability. The intake of soil-associated microorganisms was shown to contribute to the resilience of the gut microbiome against pathogens.

Living Ecosystems and Social Groups

Horses are social animals, and their natural behavior includes living in herds and interacting with their environment. Regular social interactions and environmental exposures are crucial for equine mental and physical health. The presence of other horses and a stimulating environment can influence gut microbiota positively.

A study by Parker et al. (2020) demonstrated that horses kept in social groups had a more balanced gut microbiome compared to those isolated. Social interactions and shared microbiota among herd members were found to contribute to gut health and overall well-being.

Limitations of Sterilized Living Environments and Ultra-Processed Diets

a) Sterilized Paddocks and Stalls

Housing horses in sterile environments with minimal exposure to natural elements can detrimentally impact their gut. Sterilized paddocks and stalls lack the microbial diversity necessary to support a healthy gut microbiome.

Research by Costa et al. (2012) found that horses kept in clean, isolated environments had a less diverse gut microbiota compared to those in natural, mixed settings. This reduced microbial diversity is associated with a higher incidence of gastrointestinal issues and reduced overall health.

b) Ultra-Processed Feed and Limited Hay Sources

Feeding horses a diet primarily composed of ultra-processed feeds and a single source of hay can lead to nutritional deficiencies and a less diverse gut microbiome. Processed feeds often lack the natural fibers and variety necessary for optimal gut health.

A study by Kienzle and Zeyner (2010) showed that horses fed a diet high in processed feeds had lower microbial diversity and were more prone to colic and other digestive disorders. The lack of dietary variety restricts the growth of beneficial microbes and can lead to an imbalance in the gut flora.

The Truth?

While it’s not always convenient for us, the link between diet, environment, and equine gut health is well-established through scientific research. We all know it, but do we practice it? This is the forbidden question that we all need to ask ourselves…

A diverse diet, natural soil intake, and social interactions are critical for preventing gut disease in horses. Conversely, sterile environments and ultra-processed diets pose significant limitations to gut health, highlighting the importance of natural living conditions and varied diets for horses. For optimal health, it is essential to mimic the natural conditions under which horses evolved, promoting a diverse, balanced, and interactive environment.

Are you meeting your horses’ needs in these ways?


  • Costa, M. C., Arroyo, L. G., Allen-Vercoe, E., Stämpfli, H. R., Kim, P. T., Sturgeon, A., & Weese, J. S. (2012). Comparison of the fecal microbiota of healthy horses and horses with colitis by high throughput sequencing of the V3-V5 region of the 16S rRNA
  • Dougal, K., Harris, P. A., Edwards, A., Pachebat, J. A., & Proudman, C. J. (2013). A comparison of the microbiome and the metabolome of different regions of the equine hindgut. FEMS Microbiology Ecology86(2), 343-356.
  • Kienzle, E., & Zeyner, A. (2010). Dietary effects on fermentation processes in the equine large intestine and its clinical relevance. Veterinary Clinics of North America: Equine Practice26(3), 499-514.
  • Parker, R. A., Becker, A. A., & Gardner, D. S. (2020). Influence of housing and social conditions on the fecal microbiota of horses: A preliminary study. Animals10(9), 1618.
  • Schwarm, A., Dettling, C., Pellikaan, W. F., Gabel, G., & Wittenburg, D. (2015). Fecal microbiota of horses in response to dietary supplementation with cellulose, pectin, and lignin. Journal of Animal Science93(8), 3487-3502.