Results in dry matter losses.
Horse owners have resorted to soaking hay in water to remove water-soluble carbohydrates to manage horses diagnosed with laminitis or Polysaccharide Storage Myopathy (PSSM). Researchers have suggested that complete rations (hay, grain and supplements) contain less than 12 and 10% nonstructural carbohydrates (NSC), which are the starches and sugars in the forage, for horses affected with laminitis and PSSM, respectively. The objectives of this research, conducted by faculty at the University of Minnesota, was to determine the impact of water temperature and soaking length on the removal of carbohydrates and dry matter (DM) from alfalfa and orchardgrass hays.
Hay types included bud and flowering alfalfa, and vegetative and flowering orchardgrass. Flakes were submerged for 15, 30 and 60 minutes in 7 gallons of cold (72°F) and warm (102°F) water and for 12 hours in cold water.
Prior to soaking, both alfalfa hays were below the 10 and 12% NSC recommended for horses diagnosed with PSSM and laminitis, respectively, and would not have required soaking. This is common for alfalfa, since legumes store their carbohydrates as starch, compared to grasses that store their carbohydrates as fructans (a sugar). The orchardgrass hays were above these recommendations (approximately 14% NSC pre-soaking), however, after soaking for 15 to 30 minutes, were at or below 10 to 12% NSC.
Dry matter losses were similar among all hays after soaking for 15, 30 and 60 minutes in either warm or cold water. Dry matter losses after soaking for 12 hours were greater than other treatments.
Owners should rely on forage analysis, both before and after soaking, as the primary method of determining the appropriate hay for horses, especially when feeding horses diagnosed with laminitis and PSSM. Soaking hay for short durations (15 to 60 minutes) is an acceptable management method, but should only be used if preferred hay is not available. Soaked hay should be fed immediately to reduce the chance of mold.