Effect of Hay Soaking Duration on Metabolizable Energy, Total and Prececal Digestible Crude Protein and Amino Acids, Non-Starch Carbohydrates, Macronutrients and Trace Elements.
Authors: Bochnia M, Pietsch C, Wensch-Dorendorf M, Greef M, Zeyner A
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Nutrient Loss from Hay Soaking Soaking hay is widely recommended to reduce dust and water-soluble carbohydrates for horses with respiratory disease or metabolic syndrome, yet the full nutritional consequences remain poorly characterised. Bochnia and colleagues soaked four batches of meadow hay for 0, 15, 30, 60 minutes and 12 hours at 20°C, then measured digestible protein, amino acids, energy, macronutrients and trace elements using standardised equine digestibility protocols. Just 15 minutes of soaking triggered substantial nutrient depletion: metabolizable energy dropped 5–15%, prececal digestible crude protein and amino acids both fell by approximately 35%, and prececal digestibility declined by up to 49% (from 56% unsaturated), whilst longer soaking durations produced no additional loss. Although crude fibre and lignin content paradoxically increased, the overall effect was a marked reduction in bioavailable nutrients across all categories measured, including essential minerals. For practitioners managing horses with equine asthma or metabolic syndrome, this finding presents a genuine practical dilemma: while soaking effectively addresses respiratory and glycaemic concerns, clinicians must now account for significant nutritional recalibration when formulating rations to maintain energy and protein intake, particularly in animals where marginal nutritional status or weight maintenance is already challenging.
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Practical Takeaways
- •Soaking hay effectively reduces WSC and minerals for respiratory and metabolic conditions, but practitioners must account for 5-15% loss of metabolizable energy when calculating feed portions to prevent unintended weight loss
- •A 15-minute soak is as effective as longer durations (up to 12 hours) for reducing problematic nutrients; extended soaking offers no additional benefit but increases practical labor without improved outcomes
- •For horses requiring soaked hay due to EA or EMS, increase hay volume by approximately 10-15% post-soaking and consider supplementing prececal digestible protein and amino acids to meet nutritional requirements, particularly for performance or growing horses
Key Findings
- •15 minutes of hay soaking significantly reduced water-soluble carbohydrates, macronutrients, and trace elements across nearly all investigated nutrients
- •Metabolizable energy decreased by 5-15% and prececal digestible crude protein and amino acids fell by 35% after soaking
- •Prececal digestibility declined by up to 49% compared to 56% before soaking, with longer soaking durations providing no additional wash-out benefit
- •Crude fiber and acid detergent fiber content increased while nutrient bioavailability declined substantially, posing risks for maintaining caloric and protein requirements in horses with EMS and EA