Identification of a core bacterial community within the large intestine of the horse.
Authors: Dougal Kirsty, de la Fuente Gabriel, Harris Patricia A, Girdwood Susan E, Pinloche Eric, Newbold C Jamie
Journal: PloS one
Summary
# Editorial Summary: Core Bacterial Community in the Equine Large Intestine Understanding the composition of the equine hindgut microbiota is fundamental to comprehending both digestive health and disease susceptibility, yet the structural organisation of these microbial communities remained poorly characterised. Using 454-pyrosequencing of 16S rDNA from samples across the terminal ileum and seven large intestine regions in ten horses, Dougal and colleagues identified a stratified core bacterial community with distinct regional signatures: the ileum harboured a dominant core comprising just seven operational taxonomic units (OTUs) accounting for 32% of sequences (notably Lactobacillaceae-dominated), whilst the large intestine possessed a markedly different core structure with 5–15% of sequences distributed across numerous low-abundance OTUs, with Lachnospiraceae and Prevotellaceae predominating in proximal and distal regions respectively. The critical finding is that the hindgut core is composed of many organisms present in minimal numbers rather than a few abundant keystone species—a structural arrangement that may account for the horse's well-documented vulnerability to digestive disturbance when microbial balance is disrupted. For practitioners, this work suggests that seemingly minor alterations to diet, antimicrobial exposure, or management can destabilise a precarious microbial equilibrium, and reinforces the importance of gradual dietary transitions and minimising unnecessary stressors to digestive health. This foundational work provides the baseline for understanding why horses require such careful management of their hindgut environment compared with other species.
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Practical Takeaways
- •The equine hindgut microbiota is composed of many low-abundance bacteria rather than a few dominant species; disruptions to this delicate balance through diet changes, antibiotics, or stress may trigger digestive problems.
- •Understanding that different regions of the hindgut have distinct microbial communities suggests management strategies should consider effects on the entire gastrointestinal tract, not just one area.
- •The identified core microbiota composition provides a baseline for future research into probiotics, prebiotics, and dietary management to support digestive health in horses.
Key Findings
- •A core bacterial community exists in the equine large intestine composed of many low-abundance operational taxonomic units (OTUs), distinct from the ileal community which is dominated by fewer, higher-abundance OTUs.
- •The ileal core comprises 32% of sequences from 7 OTUs dominated by Lactobacillaceae, while the large intestine core comprises only 5-15% of sequences from many more OTUs.
- •Distinct bacterial signatures exist between proximal large intestine (dominated by Lachnospiraceae) and distal large intestine (dominated by Prevotellaceae).
- •The complexity and low-abundance nature of the large intestine core microbiota may explain the horse's susceptibility to digestive upset.