For many years now, horse owners have been soaking hay to manage horses diagnosed with laminitis, Polysaccaride Storage Myopathy (PSSM), hyperkalemic periodic paralysis (HYPP) and chronic obstructive pulmonary disease (COPD), but is soaking hay really beneficial?
Soaking hay in water has been known to be a common strategy used to manage the nutritional requirements of some diseased horses. Currently, the hay soaking recommendations are to soak hay for 30 minutes in warm water, or 60 minutes in cold water, for the removal of carbohydrates (Watts,2003). However, how efficient is hay soaking and are additional essential nutrients lost during this soaking process?
University of Minnesota researchers actually conducted several tests to determine the impact of water temperature and hay soaking duration on the actual removal of non structural carbohydrates (NSC), crude protein (CP), minerals and dry matter (DM) from alfalfa and orchard grass hays. In this test, four hay types were soaked by submerging individual flakes for 15, 30 and 60 minutes in 25 liters of cold (72F) and warm (102F) water and for 12 hours in cold water and this was compared to a control non-soaked sample. Water temperatures were determined by using the cold or hot only faucets which would be typical of your standard barn.
Researchers have suggested that diets for horses affected with laminitis (Frank, 2009) should be less than 12 - 10% of NSC value. Reynolds et al (1997) also established that a diet of less than 1% K is necessary for horses diagnosed with HYPP and Moore-Colyer (1996) discovered that soaking hay for 30 minutes reduced respiratory problems for horses diagnosed with COPD or heaves. It was determined that alfalfa hays were tested to be below the 10 and 12% NSC threshold for those horses diagnosed with PSSM and laminitis, so soaking these hays wouldn't be necessary. However, orchard grass hays were well above these thresholds and after soaking for 15 to 30 minutes, the NSC values were reduced to or below the 10 to 12% recommended value. It is very interesting to note that soaking hay for longer durations did not further reduce the NSC content of the hay.
During the soaking process Calcium (CA) is not as prone to leaching as compared to other minerals while Magnesium (Mg) and phosphorus (P) levels were reduced in all hay types as a result of soaking, with longer soaking times, leading to a greater reduction in these elements. Because Ca is not as water soluble as P, high Ca:P ratios were observed in soaked hays for longer times especially those after 12 hours. Ideally the Ca:P ratio should range between 1:1 and 3:1 (up to 6:1)in horse diets (NRC, 2007) but it was observed that there was a significant deficiency in P.
In conclusion, it has been noted that hay should not be soaked for greater period than 1 hour as soaking hay for any longer durations resulted in severely reduced NSC content, high Ca:P ratios, shortage of P in the diet and significant losses in DM. It was highly recommended that owners should rely on forage analysis as their first method of finding appropriate hay for horses, especially when feeding horses diagnosed with a disease and once values have been determined to take preventative measures. It has been recommended that hay soaking for short durations of 15 - 30 minutes is an acceptable hay management method, but should only be used if suitable hay is not available.