Scientific Aspects of Silage Making

Silage is a common way of storing and feeding forage in the United States. There are 4 phases (aerobic, anaerobic, stable, and feedout) that silage undergoes. The most critical phases to manage to minimize nutritive losses are when the silage is going from an aerobic to an anaerobic environment and at feedout. The first important step in achieving silage of high nutritive value is to harvest at the proper maturity and moisture level. Alfalfa should be harvested between mid bud and one-tenth bloom, and corn should be harvested between one-half and two-thirds milkline. The type of silo (pile, bunker, bag, or upright) has an impact on silage DM lost during storage. Bunker silos and piles usually have higher silage DM loss than bag and upright silos primarily because there is a greater amount of surface area exposed to oxygen. Limited research suggests that the nutritive value of high DM corn silage (~38%) can be preserved better (increased milk production) in a bagged silo system compared to a bunker silo. Filling bunker silos rapidly using the progressive wedge technique has been shown to improve the nutritive value of silage. Covering bunker silos with polyethylene plastic also improves the amount of silage DM recovered and the nutritive value of both hay crop and corn silage. During the feedout phase it is important to feed approximately 5 inches or more from the silo face each day to minimize losses in quality that occur when silage is exposed to oxygen.