Soaking Hay for Short Durations Can Help Tailor Nutrient Composition
Soaking hay in water is a common strategy to manage the diets of horses with various health conditions. Horses with chronic obstructive pulmonary disease (COPD; also known as heaves) are sensitive to dust. For this reason, soaking hay in water for about 30 minutes helps to reduce the prevalence of dust particles and can be subsequently fed to horses with respiratory issues.
Horses with laminitis, equine metabolic syndrome (EMS), equine pituitary pars intermedia dysfunction (PPID; also known as equine Cushing’s disease), or polysaccharide storage myopathy (PSSM) are very sensitive to dietary intake of sugars, such as non-structural carbohydrates (NSC). Diets high in NSC can exacerbate laminitis and aggravate muscle pain in horses with PSSM. We have discussed in a previous blog how soaking cool-season grass hays in water effectively lowers NSC, rendering them as more suitable hays that can be fed to sugar-sensitive horses.
Hyperkalemic periodic paralysis (HYPP) is caused by a genetic mutation (for a review, see blog first published on October 19, 2011). Horses with HYPP are sensitive to dietary intake of potassium (K) and exposure to stress or consumption of diets high in K may trigger attacks of muscle trembling and eventual paralysis. In order to lessen the incidence and severity of paralysis caused by HYPP, these horses must be fed diets that are low in K. Some feeds are inherently low in K and can be fed safely to horses with HYPP; however, the potassium levels in some hays are too high and should not be offered to horses with HYPP. Soaking hay in water may help to decrease K concentration.
Sugars and potassium levels in hays are reduced after soaking in water. One might then pose the question: what happens to concentrations of crude protein (CP) and other minerals, such as calcium (Ca), phosphorus (P), and magnesium (Mg) as a result? A group of researchers from the University of Minnesota recently conducted an experiment to discover what happens to those nutrients in alfalfa and orchardgrass hays after soaking. Hays examined included bud and flowering alfalfa and vegetative and flowering orchardgrass. In order to mimic resources commonly available to horse owners, flakes of hay were soaked in cold or warm water for 15, 30, and 60 minutes, or 12 hours in cold water. Hays were subsequently analyzed by a laboratory to determine how nutrient compositions were affected by soaking. Changes in CP and Ca levels were variable and depended on forage type, maturity, and soaking durations. Soaking had no effect on CP in bud alfalfa or orchardgrass flowering hay, but increased with soaking length in vegetative orchardgrass and decreased with soaking duration in flowering alfalfa hay. Calcium levels in flowering alfalfa and orchardgrass were unaffected by soaking, while Ca decreased in hays harvested at early stages of maturity (alfalfa bud, vegetative orchardgrass). In comparison, P, K, and Mg levels decreased with longer soaking times.
Soaking alfalfa and ordhardgrass hays for short durations (15 – 60 minutes) did not result in nutrient deficiencies for horses used for light work. Assuming that NSCs are reduced to acceptable levels, alfalfa hay soaked for a short time can be used to manage horses with laminitis or PSSM. Soaking alfalfa and orchardgrass hays for 12 hours was required to reduce K to levels recommended for horses with HYPP. However, P also decreased to insufficient levels, resulting in high Ca:P ratios, which would therefore require supplemental P to correct this problem. In light of this fact, owners should rely on laboratory analyses to select the appropriate hay for horses with special nutritional needs. Nutrient composition can be adjusted by soaking hay in water for short durations, while long soaking durations should be avoided because the Ca:P ratio may be adversely affected.
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Martinson, K.L., M. Hathaway, H. Jung, and C. Sheaffer. (2012). The effect of soaking on protein and mineral loss in orchardgrass and alfalfa hay. J. Equine Vet. Sci. Article in Press.