Postharvest Changes in Alfalfa Quality

Alfalfa losses and quality changes begin as soon as the mower contacts the standing crop and these losses continue until the preserved feed is consumed. Harvest losses are caused by plant respiration, rain, and mechanical damage by equipment. Loss from plant respiration is relatively small when the crop is dried quickly under good drying conditions, but under slow drying conditions it can be up to 7% of the crop dry matter (DM). When rain damage occurs, the resulting losses can be as much as 30% of the crop dry matter, and of course, at times the whole crop is lost. Mechanical losses increase as more machinery operations are used. For example, a raking operation can reduce the crop yield 5% with some of this loss being the more nutritious leaves. All of these losses, but especially respiration and rain damage, reduce the concentrations of digestible nutrients and increase the fiber content in the remaining forage. Losses and quality changes are small when dry hay is stored in a shed, but when stored outside, DM losses can be 15% or more. Lost DM is protein and other highly digestible nutrients. Silage DM losses generally range from 5 to 15% depending on the type of silo used and other management practices. This loss again comes from the most nutritious portions of the forage, and much of the crop protein is converted to non protein nitrogen, which has less value to the animal. These quality changes can reduce the intake and production of animals consuming the forage.