As understanding of equine gut health continues to evolve,
increasing attention is being focused on the relationship between diet and the
horse’s hindgut microbiome. The microbial community structure (MCS) within the
hindgut plays a critical role in fibre digestion, nutrient utilisation, immune
support, and overall gastrointestinal health. Although numerous commercial
feeds and supplements are marketed to support digestive function and optimise
nutrition, relatively little research has examined how these products influence
the equine hindgut microbiome.
Newly published research conducted by K.J. Hart, M.J. Hegarty, E.H. Hart at Aberystwyth University sought to address this knowledge gap by investigating the effects of a complementary fibre-based forage feed* on hindgut fermentation and microbial community structure under controlled laboratory conditions.
The study aimed to evaluate how the feed influenced fermentation profiles and microbial populations when added to two contrasting basal diets: a forage-only diet (FOR) and a mixed forage-and-concentrate diet (MIX). Researchers used an in vitro hindgut fermentation model designed to simulate conditions within the equine large intestine.
While in vitro systems cannot replicate every aspect of the living horse, they provide valuable tools for studying microbial activity under carefully controlled conditions. These laboratory models allow researchers to isolate dietary effects without the many variables present in live-animal trials. However, the authors acknowledged that such systems cannot fully reproduce the complexity of the equine gastrointestinal tract, including immune responses, intestinal motility, hydration dynamics, stress, exercise, and long-term microbial adaptation.
Using a 2 × 2 factorial design, the researchers examined fermentation characteristics and microbial community changes in vessels receiving either the forage-only or mixed diet, with or without inclusion of the fibre-based feed. Each treatment was replicated three times. Artificial saliva was continuously infused into the fermenters, and feed bags were incubated for 24 and 48 hours to assess microbial community structure.
The study demonstrated clear differences between the two basal diets. The MIX diet produced a lower hindgut pH and higher total volatile fatty acid production compared to the forage-only diet, indicating altered fermentation activity. These findings reinforce existing knowledge that concentrate inclusion can significantly influence hindgut fermentation patterns.
Researchers also identified significant differences in microbial community composition between the two diet types at both 24 and 48 hours. In particular, an interaction involving Proteobacteria was observed at 24 hours, with levels highest in the MIX diet supplemented with the fibre-based feed. However, beyond this isolated interaction, the inclusion of the forage feed caused no substantial additional changes to the overall microbial community structure.
Importantly, the researchers concluded that the fibre-based feed produced “no negative effects” on fermentation parameters or microbial composition within the in vitro model. In practical terms, this suggests the feed was compatible with normal hindgut fermentation processes and did not disrupt microbial balance under the conditions tested.
The findings are significant because they contribute to a growing body of research examining how equine diets influence gut microbial ecology. However, the authors’ conclusions remained appropriately cautious. The study did not evaluate live horses, clinical health outcomes, performance measures, or long-term feeding effects. Instead, it provided an initial laboratory-based assessment of how a fibre-based feed interacts with hindgut fermentation systems.
Overall, the research suggests that inclusion of the tested fibre-based forage feed did not adversely affect hindgut microbial activity in vitro, while also highlighting the substantial influence that basal diet composition exerts on equine fermentation dynamics and microbial community structure.
*EquidGel®
For more details, see:
K.J. Hart, M.J. Hegarty, E.H. Hart,
An investigation into the impact of the inclusion of a commercial fiber-based feed, designed for both hydration and nutrition, on the equine hindgut microbiomes,
Journal of Equine Veterinary Science (2026) Vol 161, 105862,
https://doi.org/10.1016/j.jevs.2026.105862
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