One dairy Bolsen worked with had a packing density of only 11.4 pounds of DM per cubic foot and an estimated shrink loss of 22.5 percent. By utilizing the University of Wisconsin Extension spreadsheet to predict density and making changes from year one to year two that included reducing the maximum height of the pile from 16 to 14 feet, adding a second pack tractor and reducing the layer thickness from 8 to 5 inches, Bolsen says the dairy was able to increase its average silage density to 16.4 pounds of DM per cubic foot and reduce its shrink loss to about 15 percent.
Other steps to consider when working to achieve a higher silage density include properly training employees who will be operating the push-up and pack tractors; forming a progressive wedge of forage and maintaining a maximum slope of 1 to 4 (1 foot of rise for each 4 feet of horizontal); increasing the weight of all push-up and pack tractors; passing over each layer of forage at least twice; packing drive-over piles from side to side; and driving up and backing down progressive wedge and side slopes to avoid making 180-degree turns on a forage surface, floor of a bunker or front apron of a pile. In bunker silos it is also necessary to increase the numbers of tractor passes near the wall to reach a high density in the forage that is within 3 feet of the wall.
Enhancing silage sealing
Once the forage is densely packed, the next step to reducing silage DM loss is to apply an effective seal to the bunker or pile. Bolsen says while it is inevitable that oxygen will get into the silage over time, utilizing an oxygen barrier film can reduce shrink loss in the outer 2 to 3 feet of corn silage by 40 to 50 percent or more compared to standard white-on-black plastic.
He says the film clings to the surface of the silage and fills the air pockets to better seal the silage. In a 3,000-ton-capacity bunker silo of corn silage that is 50 feet wide and 225 feet long with an average depth of 12 feet, sealing with an oxygen barrier film would save an extra $2,500 to $4,500 of silage in the original top 3 feet compared to standard plastic. In a 4,000- to 4,500-ton-capacity drive-over pile of corn silage that is 80 feet wide at the base and 400 feet long with an apex height of 12 feet, sealing with an oxygen barrier film would save between $5,000 and S10,000 of corn silage in the original top 3 feet compared to standard plastic. Bolsen says he’s seen DM losses as low as 8 to 10 percent on beef and dairy operations that utilize oxygen barrier film to seal silage.