38 EQUINE
Examining the equine gut microbiome
T
he equine gut microbiome represents an extremely complex microbial ecosystem that is comprised of quadrillions of microorganisms. These microorganisms include bacteria, yeast, fungi and protozoa. Bacteria are thought to play the most important functional role. This microbial community not only impacts the equine digestive tract but also plays an instrumental role in immune and endocrine response, cognitive function and behavior. Researchers have been working for many years to identify specific gut microbes
and learn more about their functionality in order to further understand the role of the equine digestive system in both disease prevention and treatment. “Studying the equine intestinal microbiome is important because horses are hindgut fermenters,” said Scott Weese, DVM, M.Sc., Dipl. ACVIM, a professor in the department of pathobiology at the University of Guelph’s Ontario Veterinary College. “Changes in the microbiome can result in diseases such as colic, colitis and laminitis, which are leading causes of morbidity and mortality in horses.”
Influential factors
Each horse’s gut is unique to them, with the microbiota structure beginning to take shape within the first few days of life. The overall gut microbiome is influenced by several factors, including age, genetics, diet, exercise, stress, body condition and the horse’s environment. Interestingly, the microbiomes of wild horses include a more diverse spectrum of microbiota than domesticated horses (Fig. 1). Beyond age, differences in housing and pasture habits, the composition of their feeding diets, contact with humans, veterinary healthcare and medication seem to be among the most influencing factors for equine microbiomes (Kauter, A., Epping, L., Semmler, T. et al., 2019). At present, scientists believe that hindgut microbiota are largely responsible for:
The microbiomes of non-domesticated horses (left) include a more diverse spectrum of microbiota compared to those of domesticated horses (right).
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• Fiber digestion and the breakdown of structural carbohydrates, such as those found in grass, hay, beet pulp and other forages. This process results in the production of volatile fatty acids, which are then converted to energy. Hindgut forage fermentation provides up to 70% of a horse’s energy requirements. • Enhancing immune functions by helping to neutralize potential toxins and protect the horse from an overgrowth of pathogenic organisms. For example, an overabundance of Proteobacteria is reported OCTOBER-DECEMBER 2020
