More on the Equine Microbiome

Contributed by Ashleigh Flores, M.S.

Within the GI Tract, horses can host up to 1015 bacterial cells, with the highest population residing within the caecum. Recent studies have revealed that distinct individual ecosystems for each compartment of the equine gut exist, with adjacent compartments having the most similarities in microbiome composition. The upper GI tract shows a more variable microbiota compared to the lower GI tract, likely due to a high throughput of environmental bacteria present in forage. Members of the α-Proteobacteria such as Methylobacterium sp., Rhizobium sp. and Sphingomonas sp. are commonly abundant in the upper GI tract while Firmicutes, Bacteroidetes and Verrucomicrobia have been found to be amongst the predominating phyla in the equine hindgut. It is thought that changes in the microbiome are strongly associated with the development of colic in horses. At present, there is a lack of data regarding the equine microbiome, further research in this area is needed for improved treatment and prevention of equine GI tract diseases.


Kauter, A., Epping, L., Semmler, T. et al. The gut microbiome of horses: current research on equine enteral microbiota and future perspectives. anim microbiome 1, 14 (2019).

Costa MC, Silva G, Ramos RV, et al. Characterization and comparison of the bacterial microbiota in different gastrointestinal tract compartments in horses. Vet J. 2015;205(1):74-80. doi:10.1016/j.tvjl.2015.03.018

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