Stability of Gastric Fluid and Fecal Microbial Populations in Healthy Horses under Pasture and Stable Conditions.
Authors: Bishop Rebecca C, Kemper Ann M, Clark Lindsay V, Wilkins Pamela A, McCoy Annette M
Journal: Animals : an open access journal from MDPI
Summary
Understanding the baseline microbial ecology of the equine stomach and colon is essential for identifying pathological shifts associated with gastric and colonic disease, yet the composition and temporal stability of gastric microbiota in healthy horses remains poorly characterised. Bishop and colleagues examined microbial communities in gastric fluid and faecal samples collected weekly from healthy horses over a 16-week period spanning pasture grazing (6 weeks), stable confinement (5 weeks), and return to pasture, with consistent forage provision throughout. Whilst gastric fluid harboured substantially fewer bacterial taxa than faeces (770 versus 5284 species), both compartments demonstrated compositional stability within each management condition, with no significant week-to-week variation in either location; housing transition did trigger predictable shifts—notably increased Lactobacillaceae and decreased Streptococcaceae in gastric fluid when moving indoors, paralleled by increased faecal Firmicutes and reduced Bacteriodota. These findings establish a baseline of normal microbial stability that practitioners can reference when evaluating horses with suspected foregut disease, suggesting that acute or sustained deviations from an individual's typical gastric microbiota profile may warrant clinical investigation. The characterisation of this healthy steady-state offers a foundation for future research into dysbiosis-associated conditions such as equine gastric ulcer syndrome and could ultimately inform targeted dietary or probiotic interventions.
Read the full abstract on PubMed
Practical Takeaways
- •Gastric and fecal microbial populations are stable within each management condition, providing a baseline to identify abnormal microbial shifts associated with foregut disease in clinical cases
- •Housing changes (pasture to stable or vice versa) alter microbial composition measurably; this should be considered when evaluating horses with gastrointestinal issues during management transitions
- •Understanding normal microbial stability in healthy horses enables better recognition of dysbiosis-related problems, potentially informing preventive management strategies for gastric and colonic health
Key Findings
- •Gastric fluid contained significantly fewer taxa (770) compared to fecal samples (5284), with species richness and diversity differing significantly between sample types (p < 0.001)
- •Housing conditions (pasture vs. stable) significantly affected microbial composition in both gastric fluid and feces (p = 0.005 and p = 0.001 respectively), with Lactobacillaceae increasing and Streptococcaceae decreasing in gastric fluid when moving to stable
- •Within each housing condition, microbial populations remained stable week-to-week with no significant variation in gastric (p = 0.9) or fecal (p = 0.09) microbiota despite consistent forage diet
- •Fecal Firmicutes increased while Bacteriodota decreased when horses transitioned from pasture to stabled conditions