Researchers explore equine gut microbiota and microbial activity

Equine medical researchers have discovered the intestinal tract plays a crucial role in a horse’s overall health, and they are focusing on the diversity of the gastrointestinal microbiome. 

Shortly after it is born, a foal begins to develop its microbial foundation, which is shaped by its environment and the influence of its mother. 

As the foal grows, additional elements of this microbial blueprint are established, and research indicates, early in life, the fecal microbiome of the foal is significantly different from its mother. 

However, within a short period of time, the microbial profiles of the mare and foal become quite similar.

Research has shown every part of a horse’s gastrointestinal tract has a unique microbiome, which consists of specific populations of microorganisms. 

As studies have progressed, the connection between the microbiome and overall health has become increasingly evident. 

Changes in the microbiome have been linked to various health issues, including laminitis, equine metabolic syndrome, colitis, colic and inflammatory bowel disease. 

Even more intriguing is the discovery of complex communication pathways between the host – the horse – and the microbes within its gut. 

This communication is highlighted by the microbiome’s influence on immune function, inflammation and cognitive function and behavior.

Researching microbiome

According to research, a horse’s gastrointestinal microbiome is the community of microorganisms living in its digestive tract. 

This microbiome, which consists of bacteria, archaea, protozoa, fungi and viruses, is essential for a horse’s digestion, metabolism and immune system.

“These intestinal microbial residents affect local mucosal immunity, produce short-chain fatty acids for energy and develop tolerance to antigens,” states a Feb. 18 EquiManagment article by Veterinarian Dr. Nancy Loving. “As a whole, these features help define a horse’s well-being.” 

Loving states, “Immune modulation in the horse’s intestines accounts for 60 percent of the body’s immune function, signifying a balanced microbiome and its bacterial byproducts are essential for metabolic health, while the gut-brain axis significantly influences a horse’s behavior.”

Researchers have now expanded their studies to explore the metabolic effects of gut microbiota.

“While the diversity of bacterial species within a horse’s intestinal tract is important, each horse is an individual with differing bacterial constitutions,” she notes. “Further, these bacteria are in a constant state of change depending on the food ingested, the horse’s environment, medication given, season and daily stressors.”

Researchers are no longer looking at the collection of which individual bacteria inhabit the gastrointestinal tract but are instead looking at the products of microbial activity and subsequent function, referred to as the metabolome. 

Loving adds, “These are smaller molecules resulting from digestion of what a horse has consumed, including medications, and these molecules are important in cell signaling processes from chemicals they produce.”

The intestinal bacteria expressed is referred to as metatranscriptome, which describeed the RNA and identifies which genes are “turned on,” Loving explains.

Another area of current research is the exfoliome, which refers to the cells shed from the intestinal lining as a natural part of epithelial renewal. Researchers can identify the genes expressed by the epithelial cells lining the gastrointestinal tract by analyzing the mRNA found in feces.

Feeding the microbiome

The goal of feeding the microbiome is to nurture beneficial gut bacteria. Feeding involves not only nutrition but also exercise, medications, a horse’s environment, daily routines, tasks, travel, competition and stress.

Loving states, “Diet is a key element in feeding gut microbiota. In another recent study, researchers examined management strategies to prevent gut dysbiosis in horses.”

According to research, for optimal gastrointestinal health of the microbiome, at least 60 percent of a horse’s diet should be high-quality forage, which promotes good function of the bacteria that ferment fibers to produce short-chain fatty acids such as butyrate and help maintain stable bacterial communities. 

“Processed grains and concentrates should be limited as much as possible due to poor small intestinal digestion which causes them to spill over into the large colon where they ferment to cause acidosis and bacterial cell death,” she adds. 

However, supplementation with prebiotics, probiotics and postbiotics can affect intestinal bacterial health.

Current research notes prebiotics, psyllium, beet pulp, fructo-oligosaccharides from plants and good-quality forage are useful as they are fiber-based and can provide nutrition to existing and beneficial gut microorganisms.  

Loving explains, “An example of probiotics includes live organisms such as saccharomyces, lactobacillus, bifidobacterium and enterococcus, which are lactic-acid-producing bacteria.” 

Yeast has probiotic functions for fiber digestion, while saccharomyces might provide the best benefits to microbiota modulation, based on study results. 

Researchers have identified numerous probiotics, but reliable evidence supporting their effectiveness is still lacking. 

Live organisms may struggle to survive the acidity of the equine stomach, which hinders their ability to reach and colonize the large colon where they are needed. Additionally, fermentation in the cecum may further reduce their viability.

“Postbiotics are metabolites and soluble byproducts like butyrate produced by gut microorganisms after feeding on fiber,” she adds. “Butyrate provides energy and nutrition to intestinal epithelial cells to further strengthen tight junctions between the cells, optimizing the gut barrier’s integrity to prevent leaky gut syndrome.” 

In the future

Researchers continue to examine metabolomic data from within the equine microbiome to identify biomarkers indicating leaky gut problems. 

“This information will help veterinarians and nutritionists tailor a diet specific to a horse’s needs to favorably alter gut microbiome bacteria and affect the metabolome products’ activity and function,” Loving mentions. 

Specific diets can promote the proliferation of favorable bacteria and the production of their metabolites, stabilizing intestinal pH and other environmental factors critical to ensuring a healthy microbial balance in the equine gut, contributing to the horse’s overall health.  

Melissa Anderson is the editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.