The Fibre Requirements of Horses and the Consequences and Causes of Failure to Meet Them.
Authors: Ermers Colette, McGilchrist Nerida, Fenner Kate, Wilson Bethany, McGreevy Paul
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Inadequate fibre intake—defined as less than 1.5% of bodyweight daily or fewer than 8 hours of foraging opportunity (with breaks not exceeding 4–5 hours)—triggers a cascade of physiological and behavioural complications that extend far beyond simple digestive discomfort. When starch replaces forage in equine diets, the consequences are substantial: in the stomach, reduced saliva production and prolonged acidity precipitate equine squamous gastric disease (ESGD), whilst in the hindgut, undigested starch destabilises the microbiota, promoting volatile fatty acid and lactic acid production that elevates acidosis and laminitis risk. Beyond gastrointestinal pathology, compromised hindgut microbiota function impairs immune competence and influences behaviour adversely through gut-brain signalling, whilst reduced saliva production simultaneously increases colic risk. This 2023 review synthesised evidence demonstrating that substituting fibre-based energy sources for starch substantially mitigates EGUS incidence, improves hindgut pH and microbial stability, enhances behavioural profiles (reducing stereotypies such as crib-biting and wood-chewing), and supports immune function and athletic performance. For practitioners across disciplines—farriers managing laminitis cases, vets addressing recurrent colic and gastric ulceration, and nutritionists formulating high-energy diets—the evidence suggests that adequate forage provision should be the foundational strategy, with supplemental fibre sources prioritised over starch when concentrated energy is required.
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Practical Takeaways
- •Ensure all horses receive minimum 1.5% bodyweight in forage daily with continuous access (no >4-5 hour gaps) to prevent gastric ulcers, hindgut acidosis, and behavioral issues
- •Replace starch-based concentrates with high-fiber alternatives (e.g., fiber-based oils, chaff, silage) when designing high-energy rations to reduce EGUS incidence and laminitis risk
- •Monitor for wood-chewing and stereotypic behaviors as indicators of inadequate forage intake or low forage quality; increase hay quantity/quality and grazing time rather than supplementing starch
Key Findings
- •Minimum forage requirement of 1.5% of bodyweight with ≥8 hours daily foraging opportunity (no >4-5 hour gaps) prevents physiological and behavioral consequences
- •Starch-based rations increase risk of EGUS, hindgut acidosis, and laminitis by reducing saliva production and causing gastric acid splashing and microbial instability
- •Fibrous alternatives to starch in high-energy diets reduce EGUS risk, improve GIT pH, body condition, immune function, and reduce stereotypic behaviors including crib-biting and wood-chewing
- •Inadequate forage intake impairs gut-brain axis signaling, compromises immune function, and increases behavioral problems including aggression and stress