Hay soaking should only be done if the horse has been diagnosed with laminitis, EMS, PSSM, and/or HYPP, and a hay analysis indicates specific nutrients are in excess of recommendations.
Questions: Should I always be soaking my horse's hay, or is this something reserved for horses with respiratory problems or other health conditions such as laminitis?
Answer: Soaking hay in water is a common strategy used to manage horses diagnosed with laminitis, equine metabolic syndrome (EMS), polysaccharide storage myopathy (PSSM), and hyperkalemic and periodic paralysis (HYPP). Soaking hay should not be done, and is not necessary, for healthy horses because essential nutrient are leached during the hay soaking process.
Hay is soaked for horses diagnosed with PSSM, EMS and laminitis to remove some of the nonstructural carbohydrates (NSC) from the forage; NSC are water soluble. Horses diagnosed with PSSM should have an overall diet of ≤10% NSC, and horses diagnosed with EMS and/or laminitis should have an overall diet of ≤ 12% NSC. Although forage is the major component of a horses diet, when feeding horses diagnosed with these diseases, make sure to account for NSC content in any grain, supplements, and treats the horse is also receiving.
Before soaking hay, it is critical to have the hay tested for nutritive value. Legumes (i.e. alfalfa) tend to be lower in NSC compared to cool-season grasses (i.e. timothy), and hays containing legumes may not need to be soaked. Soaking most grass hays for 15 to 30 minutes will remove enough NSC for horses diagnosed with PSSM, EMS, and/or laminitis. However, testing forage both before and after soaking is necessary to ensure recommended levels of NSC are being met. Soaking forage for greater than 60 minutes is rarely necessary and may actually be detrimental due to excessive leaching of essential nutrients and loss of dry matter.
For horses diagnosed with HYPP, soaking hay is water is necessary to leach potassium (K), which is water soluble. Unfortunately, legumes and cool-season grasses tend to be very high in K and often exceed the recommended 1.1% maximum over-all diet for horses diagnosed with HYPP. For horses with HYPP, soaking hay for 60 minutes is often necessary. If soaking hay for 60 minutes does not achieve the recommended amounts, owners may need to consider feeding a complete feed that formulated for horses diagnosed with HYPP.
For horses diagnosed with respiratory disease, including heaves, thoroughly wetting the hay is sufficient. Wetting the hay is different from hay soaking. The goal of wetting hay is to weigh down mold and dust particles so they are not inhaled. Horses diagnosed with respiratory problems do not have nutrient restrictions (unless they have a secondary diagnosis), and therefore, hay soaking is not necessary. Wetting the hay will have a minimal impact on leaching of essential nutrients.
Bottom line, hay soaking should only be done if the horse has been diagnosed with laminitis, EMS, PSSM, and/or HYPP, and a hay analysis indicates specific nutrients are in excess of recommendations. Thoroughly wetting the hay is necessary for horses diagnosed with respiratory disease. Soaking hay in water is not necessary for healthy horses.
For more information on hay soaking, visit http://www.extension.umn.edu/agriculture/horse/nutrition/hay-soaking/
By: Krishona Martinson, PhD, University of Minnesota