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Role of Fecal Bacteria in Equine Grass SicknessBy Kentucky Equine Research Staff · May 26, 2016

Equine grass sickness (EGS), prominent in the United Kingdom and other parts of northern Europe, remains an important, though poorly understood, cause of horse deaths each year.

Veterinary researchers now believe that EGS results from the overgrowth of Clostridium botulinum type C in the large intestine. Although a normal inhabitant of a horse’s gastrointestinal microbiome, exuberant growth of this bacterium can culminate in damaged nerves supplying the gastrointestinal tract due to bacterial production of a potent neurotoxin.

To further understand the role of C. botulinum and other bacterial population changes that occur in the intestinal tracts of horses with EGS, researchers collected fecal samples from 13 EGS and 20 unaffected horses. The bacterial DNA was collected and analyzed. They found:

  • No increase in fecal C. botulinum in horses with EGS;
  • Alterations in other bacterial populations, including increases in Bacteroidetes (such as Veillonella) and a decrease in Firmicutes bacteria.

Those changes in bacterial populations were similar to horses with colitis. Although the importance of the increase in Veillonella and lack of increase in C. botulinum remains unclear, research continues.

“In the meantime, protect horses from EGS by avoiding pastures where previous cases have occurred and overgrazing, maintaining a constant diet with no abrupt nutritional changes, and supplementation with a probiotic or hindgut buffer such as EquiShure,” recommended Kathleen Crandell, Ph.D., an equine nutritionist for Kentucky Equine Research (KER).

*Leng, J., C. Proudman, F. Blow, et al. 2015. Understanding intestinal microbiota in equine grass sickness: Next generation sequencing of faecal bacterial DNA. Clinical Research Abstracts. British Equine Veterinary Association Congress. Equine Veterinary Journal 47(Suppl. 48):8.