Chemical composition and physical characteristics of faeces in horses with and without free faecal liquid - two case-control studies.
Authors: Lindroth K M, Dicksved J, Vervuert I, Müller C E
Journal: BMC veterinary research
Summary
# Editorial Summary Free faecal liquid (FFL)—where horses produce distinctly separated solid and liquid faecal phases—remains poorly understood despite its apparent links to hindgut dysbiosis, though the precise biochemical mechanisms driving this condition have never been rigorously characterised. Lindroth and colleagues conducted two concurrent case-control studies across Scandinavia and Germany, analysing faecal samples from 82 and 64 matched horse pairs respectively, measuring dry matter content, osmolality, mineral composition, short-chain fatty acid profiles, pH, particle size distribution, and water-holding capacity to establish what distinguishes FFL faeces from normal material. Horses producing FFL exhibited significantly lower faecal dry matter and altered osmolality, along with measurable differences in mineral concentrations and SCFA production patterns, though findings showed some variation between the two geographic cohorts, suggesting either environmental or management-related influences on the condition's biochemical expression. These compositional differences provide quantifiable markers that may help practitioners identify underlying fermentation disturbances contributing to FFL, potentially opening avenues for targeted nutritional or prebiotic interventions rather than empirical treatment. The consistency of findings across two large independent datasets strengthens confidence in the fermentation hypothesis whilst highlighting that FFL likely represents a syndrome with multiple contributing factors rather than a single pathological entity.
Read the full abstract on PubMed
Practical Takeaways
- •Free faecal liquid represents a genuine alteration in hindgut fermentation and faecal composition, not merely a management or feeding issue—consider referral for veterinary investigation if observed
- •Measuring faecal dry matter and osmolality could help identify horses at risk or confirm FFL diagnosis, potentially guiding dietary or probiotic interventions
- •Persistent two-phase faecal separation warrants assessment of forage quality, water intake, and individual digestive tolerance—one-size feeding approaches may not work for affected horses
Key Findings
- •Horses with FFL showed significantly lower faecal dry matter content and altered osmolality compared to controls across both studies
- •Short-chain fatty acid (SCFA) profiles and pH differed between FFL and control groups, indicating disturbed hindgut fermentation
- •Physical characteristics including increased free liquid, altered water holding capacity, and particle size distribution were distinct in FFL cases
- •Faecal composition changes were consistent across multiple sampling periods, suggesting FFL is a persistent condition with measurable biochemical signatures