Research shows that while rained-on hay is less than desirable for beef and dairy cattle it can be good for horses, especially those with laminitis, Equine Metabolic Syndrome or obesity.
Several researchers have studied the effects of rain on cut alfalfa in the field, according to Dan Undersander, University of Wisconsin. One inch of rain can cause dry matter losses of 22%. Similar hay without rain damage loses only 6%. Reduced dry matter cuts feed efficiency in dairy and beef cattle and increases feeding costs.
Rained-on hay can be a suitable forage depending on several factors. Quality tends to be retained if rainfall: occurs soon after cutting, there is only one rain event, intensity was high and forage has not been re-wetted by more rain.
Horses prone to laminitis and other metabolic disorders can benefit by being fed rained-on due to its reduced soluble carbohydrate content. Analyzing nutrient content of rained-on hay is recommended . Ironically, purchasing rained-on hay with naturally low levels of carbohydrates is a possible alternative to soaking hay as some horse owners do to reduce carbohydrates.
Rained-on hay usually sells for less than hay not exposed to rain. So, horses might actually save money and gain a health benefit at the same time. For more information, go to www.midwestforage.org and find the December issue of Forage Focus in the archives.