Rain Damage to Forage During Hay and Silage Making by Mike Rankin and Daniel Undersander Fond du Lac County Crops and Soils Agent Forage Extension Specialist, UW-Madison Introduction Rain that occurs between the time forage is cut and harvested causes both yield and quality losses that reduce the value of the crop as an animal feed and a marketable commodity. Leaching of soluble carbohydrates, protein, and certain minerals. Leaf shattering and loss, removing the highly digestible and high protein portion of the forage. Microbial activity that metabolizes soluble carbohydrates, reduces forage energy content, and possibly produces harmful mycotoxins. Several research studies have addressed the effects of rainfall on cut alfalfa.
Losses appear to be greatest after partial drying of the forage has occurred.
In Michigan, Rotz and co-workers conducted several different studies to examine the effects of rainfall on field cured alfalfa. In a second study, rainfall intensity was kept constant at 0.7-in but spread over periods of 1 to 7 hours. Dry matter losses ranged from 4 to 13 percent with highest losses occurring when the rain was spread over a longer duration. Leaching is the movement of cell solubles out of the plant. Components of the plant that are very water-soluble are leached out of the forage and lost during a rain event.