Soaking horse hay can cut sugars, but it also strips nutrients

Soaking hay remains a common strategy for managing horses with equine metabolic syndrome, especially when clinicians or pet parents are trying to reduce water-soluble carbohydrates in forage. But the tradeoff is becoming clearer: soaking can also strip out useful nutrients, and the amount lost is inconsistent enough that experts don’t view it as a precise nutritional tool. The Horse framed the question for horse caretakers, and the broader veterinary literature supports that caution. (thehorse.com)

The practice grew out of two familiar clinical needs, reducing sugar intake for horses with EMS or laminitis risk, and, in some cases, dampening dust exposure for horses with airway disease. Current veterinary references still support soaking as an option when low-nonstructural-carbohydrate hay isn’t available. Merck says horses with EMS should ideally receive hay tested at 10% NSC, with soaking for about 60 minutes as one possible management strategy. UC Davis goes a step further, warning that while soaking can lower water-soluble carbohydrates, the actual reduction is variable enough that it’s not a reliable way to create a consistently low-NSC forage. (merckvetmanual.com)

That variability is central to the story. In a 2021 Journal of Equine Veterinary Science study, researchers soaked meadow hay for 15 minutes, 30 minutes, 60 minutes, and 12 hours. They found that even 15 minutes significantly reduced many measured nutrients, including fructans, water-soluble carbohydrates, macronutrients, and trace elements. Metabolizable energy fell by 5% to 15%, while prececal digestible crude protein and amino acids dropped by about 35%, and longer soaking did not necessarily produce a better wash-out effect. The authors concluded that soaking can negatively alter hay’s nutritional value and complicate ration formulation, particularly for horses with EMS or equine asthma. (sciencedirect.com)

Other sources broadly point in the same direction. The University of Minnesota Extension advises relying on forage tests before and after soaking when possible, because soaking for 15 to 60 minutes can help manage horses needing lower carbohydrate intake, but also changes the feed itself. Cornell’s equine team notes that if hay quality is unknown, soaking for 30 minutes before feeding may reduce water-soluble carbohydrates by as much as 50%, but they also emphasize that a hay-only diet needs mineral support. UC Davis is more direct, stating that animals fed soaked hay particularly need mineral supplementation because minerals leach into the soak water along with soluble carbohydrates. (extension.umn.edu)

There’s also a practical summer-management concern behind The Horse’s related coverage. Wet hay is more perishable than dry hay, and research on treated hay hygiene has found that storing soaked hay can increase yeasts, bacteria, and mold. That supports the longstanding advice to soak immediately before feeding, drain it, and avoid letting soaked forage sit in warm conditions. For veterinarians counseling barns during hot weather, the nutrition question and the biosecurity question are tied together. (mdpi.com)

Why it matters: For veterinary professionals, the message is less “don’t soak” than “don’t assume soaking is nutritionally neutral.” In horses with EMS, laminitis history, PPID overlap, obesity, or asthma, soaking may still be a useful workaround when ideal forage isn’t available. But it can unintentionally deepen calorie restriction, reduce protein quality, and strip minerals from already marginal hay. That means diet plans should account for dry matter loss, not just sugar loss, and should often include hay testing, ration balancing, and follow-up monitoring of body condition, insulin control, and laminitis risk. Merck and UC Davis both place diet at the center of EMS management, and both effectively treat soaking as a secondary tool rather than a substitute for forage analysis. (merckvetmanual.com)

The industry perspective is notably consistent: soaking is helpful, but imprecise. Across academic, extension, and clinical sources, the advice converges on testing hay first, using soaking selectively, and replacing lost nutrients when needed. That’s a useful takeaway for equine practices fielding routine feeding questions from pet parents who may see soaking as a simple home fix. In reality, it’s a management intervention with measurable nutritional consequences. (thehorse.com)

What to watch: The next step for clinicians and barns is likely more individualized forage management, with post-soak nutrient analysis, tighter soaking times, and greater use of ration balancers or alternative low-NSC forage options instead of blanket soaking recommendations. (sciencedirect.com)