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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #269693

Title: The effect of soaking on carbohydrate removal and dry matter loss in orchardgrass and alfalfa hays

item MARTINSON, KRISHONA - University Of Minnesota
item Jung, Hans Joachim
item HATHAWAY, MARCIA - University Of Minnesota
item SHEAFFER, CRAIG - University Of Minnesota

Submitted to: Journal of Equine Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2011
Publication Date: 6/1/2012
Citation: Martinson, K., Jung, H.G., Hathaway, M., Sheaffer, C.C. 2012. The effect of soaking on carbohydrate removal and dry matter loss in orchardgrass and alfalfa hays. Journal of Equine Veterinary Science. 32(6):332-338.

Interpretive Summary: Horses can suffer from a hoof problem known as laminitis that causes pain when walking or even simply standing. If horse feed contains too many simple sugars, then this can cause horses to develop laminitis. Forages such as grasses and legumes sometimes accumulate high concentrations of simple sugars, and horse owners often resort to soaking hay in water prior to feeding in order to remove these simple sugars. However, the actual efficacy of water soaking for removal of simple sugars has not been well established, and its impact on other nutrients and the economics of feeding horses has been ignored. When immature and mature alfalfa and orchardgrass hays were soaked for various lengths of time in cold or warm water, it was found that water temperature had little differential impact on sugar removal. Duration of soaking was important, with long soaking being more effective; however, losses of other nutrients also increased with duration of soaking. Soaking removed sugars and protein, resulting in residual hay that had more fiber. Total loss of these nutrients was substantial and could require purchasing 15% more hay in order to have sufficient soaked hay for feeding horses their required daily intake of feed. A short soak of 15 to 30 minutes was recommended to remove excess sugars but limit loss of other nutrients. These results will be of interest to horse owners and health care providers.

Technical Abstract: To manage horses affected with laminitis and Polysaccharide Storage Myopathy, owners soak hay in water to remove nonstructural carbohydrates. However, the loss of dry matter (DM) and its effect on carbohydrate concentrations after soaking has not been evaluated. The objective was to determine the impact of water temperature and soaking time on removal of carbohydrates and DM from alfalfa (Medicago sativa L.) and orchardgrass (Dactylis glomerata L.) hays. The experimental design was a randomized complete block with six replications. Hay types included bud and flowering alfalfa and vegetative and flowering orchardgrass. Flakes were placed in a mesh bag, weighed, and submerged for 15, 30, and 60 minutes in 25 liters of cold (22 C) and warm (39 C) water and 12 hours in cold water. Samples were submitted for nutrient analysis, and DM losses were determined by calculating weights of residual hay. Hay types were analyzed separately and flakes were the experimental units. Soaking duration and water temperature were considered fixed effects while replicates were considered a random effect. Significance was declared at P less than or equal to 0.05. With few exceptions, water temperature at each soaking duration did not affect residual water soluble (WSC), nonstructural (NSC) and ethanol soluble carbohydrate (ESC) concentrations of alfalfa hays. Water temperature did have an effect on orchardgrass hays. Flowering and vegetative orchardgrass hays soaked for 30 and 60 minutes, respectively, in warm water had greater (P < 0.001) amounts of WSC, NSC, ESC and fructan removal compared to soaking in cold water. Soaking duration affected carbohydrate removal. Soaking bud and flowering alfalfa and vegetative orchardgrass hays for greater than or equal to 15 minutes removed WSC, NSC, ESC, and fructan compared to the control (P less than or equal to 0.005). Soaking bud and flowering alfalfa and vegetative orchardgrass hays for 15 to 60 minutes resulted in similar removals of WSC, NSC, ESC, and fructan. Differences between the 15 and 60 minute soak were observed for flowering orchardgrass hay where the longer soaking times resulted in greater (P < 0.001) carbohydrate removal. Dry matter losses were similar among all hay types after soaking for 15, 30, and 60 minutes in either warm or cold water. Dry matter losses after soaking for 12 h were greater than other treatments (P < 0.001). Soaking hay for 15 to 30 minutes is recommended to remove sufficient nonstructural carbohydrates while minimizing DM losses. Prior to soaking hay, horse owners should take into consideration initial forage carbohydrate levels and horse disease status.