Considerations for the use of restricted, soaked grass hay diets to promote weight loss in the management of equine metabolic syndrome and obesity.
Authors: Argo Caroline McG, Dugdale Alexandra H A, McGowan Catherine M
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Soaked Hay for Equine Weight Loss Restricted hay diets are commonly recommended for overweight horses and ponies with metabolic syndrome, yet the practice of soaking hay to reduce caloric intake lacks robust clinical evidence. Argo and colleagues fed twelve overweight animals soaked hay at what was intended to be 1.25% of bodyweight daily (dry matter basis) for six weeks, whilst a subset of six animals underwent detailed digestibility trials to quantify nutrient losses from the soaking process. The cohort achieved weight loss of 0.98% of bodyweight weekly—comfortably within the target 0.5–1.0% range—though individual responses varied considerably, with the most responsive animal losing approximately 2% weekly. Critically, the researchers discovered that soaking leached water-soluble carbohydrates and ash whilst increasing the relative fibre concentration, and more importantly, that corrected dry matter provision fell to only 1% of bodyweight (rather than the intended 1.25%), inadvertently delivering just 64% of maintenance digestible energy requirements. The findings suggest that hay soaking intensifies energy restriction beyond clinical intention, which may explain accelerated weight loss but raises concerns about inadvertent over-restriction and potential metabolic or musculoskeletal consequences. The authors propose an acid detergent fibre-based correction method to allow practitioners to predict nutrient loss in individual hays and calibrate feeding management appropriately, enabling safer, more predictable weight loss protocols tailored to individual metabolic response.
Read the full abstract on PubMed
Practical Takeaways
- •Soaked hay diets do promote weight loss in obese horses (0.98% BM/week), but the mechanism is partly due to unintended severe energy restriction caused by nutrient leaching during soaking
- •Always correct the amount of soaked hay fed using the validated ADF-based method to avoid accidentally restricting energy by >20% beyond your target, which may cause welfare concerns or unexpected rapid weight loss
- •Monitor individual animals closely as weight loss sensitivity varies considerably (range ~0.5-2% BM/week); the most sensitive animals may lose weight too rapidly on this protocol
Key Findings
- •Soaked hay fed at 1.25% of body mass (dry matter equivalent) resulted in weight loss of 0.98 ± 0.10% of body mass weekly, meeting the target range of 0.5-1.0%
- •Soaking hay leached water-soluble carbohydrates and ash while increasing acid detergent fibre concentrations, with actual dry matter provision only 1% of body mass daily
- •The unintended energy restriction was 23.5% greater than planned (providing only 64% of maintenance digestible energy requirements), leading to accelerated weight loss
- •An acid detergent fibre-based correction method was validated to predict nutrient leaching and enable accurate feeding management with soaked hay