In horses, just as in people, inflammatory bowel disease (IBD) can lead to chronic diarrhea, weight loss, and pain. Although the condition’s impact on equine health and welfare is becoming more widely recognized, diagnosing it can still be tricky. Traditional diagnostic methods for IBD, including endoscopy and biopsy, are invasive for horses and costly for their owners. Could examining manure be a viable alternative? A team of researchers from Finland recently evaluated fecal microbiota composition—the diversity and composition of bacteria in the horses’ feces—as a potential biomarker for equine IBD.

How Gut Bacteria Could Help Diagnose IBD in Horses

Driven by the need for a noninvasive and cost-effective screening method for IBD, the research team analyzed fecal samples from 27 healthy horses and 49 horses previously diagnosed with IBD. They used a molecular testing method called 16S ribosomal RNA sequencing to assess the microbiota.

Gut Bacteria Differences Between Healthy Horses and Those With IBD

Their findings revealed significant differences in microbiota composition between healthy horses and those with IBD. Specifically, the researchers discovered that different bacterial types were either depleted or enriched (increased) in IBD horses. This finding suggested a potential link between gut microbiota composition and the inflammatory processes associated with IBD.

The researchers also measured fecal calprotectin levels, a protein in white blood cells used as a marker for IBD in humans, cats, and dogs, said co-author Silva Uusi-Heikkilä, PhD, a visiting scientist in the Department of Biological and Environmental Science at the University of Jyväskylä, in Finland. But they found no differences in calprotectin levels between healthy and IBD horses.

A New Way to Detect IBD in Equine Fecal Samples?

As part of their research, the authors also turned to a machine learning model to predict the likelihood of IBD based on microbiota composition. This model accurately identified IBD in 100% of cases, but Uusi-Heikkilä noted this was based on a small test set consisting of 15 samples. “A larger sample set and different sequencing batches are needed to validate the model,” she said.

 “IBD can occur in either the foregut (stomach and small intestine) or the hindgut (cecum and large colon, also referred to as the large intestine), but fecal samples mainly represent the microbiota composition of the hindgut,” said Uusi-Heikkilä, describing another potential limitation of the study. “They do not represent the microbiota composition of the foregut very well, though some human studies have shown that even if IBD occurs in the small intestine, microbiota composition from fecal samples is altered.”

Exploring More Uses for Fecal Microbiota Analysis

Uusi-Heikkilä said that in the future her team wants to explore whether the model can distinguish between IBD and other functional impairments and if fecal samples could be used to detect other gastrointestinal conditions, such as gastric ulcers.

Take-Home Message

Researchers showed that horses with IBD have significantly altered gut microbiota composition, suggesting a potential noninvasive biomarker for diagnosing the condition. The approach could change how veterinarians diagnose equine IBD, reducing their reliance on invasive and more costly procedures.