Soaking or steaming hay are commonly used to reduce the respirable dust content of hay for horses. Soaking hay is also used to wash out some of the nutrients to help control weight and reduce the glycaemic response (the increase in blood glucose levels that occurs after feeding.)
In a study conducted at the University of Guelph, Ontario, Canada, Tiana Owens and her colleagues investigated the effect of soaking or steaming on first-cut timothy – alfalfa hay. They considered the effect on nutrient content of the hay, and on feed preference and glycaemic response in a group of Standardbred racehorses.
The research team offered each of thirteen horses a choice between two of these hays for 30 minutes. Blood samples were collected to monitor the glycaemic response. The trial was repeated until each horse had been presented with all possible combinations of hay.
The researchers found that horses consumed less soaked hay than dry or steamed hay (all on a dry matter basis). Horses also spent less time eating soaked hay than dry or steamed hay.
They report that soaked hay had lower concentrations of soluble protein, non-structural carbohydrates (NSC), and potassium compared with the same dry hay. Steamed hay did not differ significantly in nutrient content from dry hay.
In this study, soaking, or steaming, the hay did not have any detected effect on the glycaemic response.
For more details, see:
Nutrient content changes from steaming or soaking timothy-alfalfa hay: effects on feed preferences and acute glycemic response in Standardbred racehorses.
Owens T, Barnes M, Gargano V, Julien L, Mansilla WD, DeVries TJ, McBride B, Merkies K, Shoveller AK.
J Anim Sci. (2019) pii: skz252.