From the June/July 2014 issue: Silage 101

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Properly preparing and managing silage can reduce losses and improve an operation’s bottom line.

A key to any successful cattle operation is sound management of the feed supply. From the cow-calf producer to the dairy or feedlot owner, this involves not just managing feed quality control but also implementing sound strategies to reduce feed losses and keeping close watch on the balance sheet. For producers who utilize silage as a feed source for their cattle, taking steps to reduce silage dry matter (DM) loss, also called shrink loss, can have a significant impact on the cost of production.

Keith BolsenKeith Bolsen consults with David Breiner at Mill Creek Ranch near Alma, Kan., as the silage contractor chops the last few loads. They comprise the “silage triangle,” which includes the beef producer, the forage grower and the silage contractor. According to Keith Bolsen, professor emeritus at Kansas State University, most of the mistakes made occur before the silage is in the ration. It is estimated that between 18 and 20 percent of 117.85 million tons of corn silage made in the United States in 2013 will be lost to shrink. At $65 per ton that’s about $1.4 billion in corn silage inventory. If shrink losses were reduced to single digits, say 9.9 percent, the loss would drop to about $750 million. Bolsen says paying attention to details and fine-tuning one’s silage program, especially with regard to increasing silage density, improving sealing technique and utilizing an inoculant, can significantly reduce DM loss and, thus, reduce the cost of feeding a ton of silage.

Maximizing silage density

Achieving a higher packing density and reducing DM loss go hand-in-hand for multiple reasons. First, more densely packed silage in a bunker silo or drive-over pile is less porous, meaning less air moves through the silage and, subsequently, less spoilage occurs. Second, a higher packing density increases storage capacity of the bunker without over-filling or decreases the height of the pile without reducing storage capacity.

Bolsen says producers should aim to achieve a silage density of about 15 to 16 pounds of DM per cubic foot and 44 to 46 pounds of fresh weight per cubic foot. Unfortunately, many beef and dairy operations are not achieving that desired silage density, and he encourages producers to use a spreadsheet developed by researchers at the University of Wisconsin Extension (bit.ly/zCfRj0) to predict packing density in advance. Two best practices for achieving higher densities are increasing the number of pack tractors and spreading forage in uniform layers that are 6 inches thick or less. Producers must remember if forage is delivered too quickly or not enough pack tractors are available, it can be difficult to achieve a uniform layer of 6 inches and to pack each individual layer before another layer of forage is added.

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.

Two other factors to consider regarding the benefits of proper sealing are the negative effects of feeding surface spoiled silage and the dangers associated with removing spoilage from the top of most bunkers and piles today. Bolsen says producers who feed surface spoilage lose production efficiency in their cattle. In a Kansas State University study, fistulated steers were fed 0 to 16 percent surface-spoiled corn silage in rations that were 87.5 percent silage and 12.5 percent supplement. The addition of surface spoilage had large negative associative effects on DM intake and organic matter digestibility, as well as neutral and acid detergent fiber digestibilities. The first increment of spoilage had the greatest negative impact, and the results clearly showed that surface spoilage reduced the nutritive value of corn silage-based rations more than was expected. When used properly, oxygen barrier film can eliminate the need to remove surface-spoiled silage.

Using an inoculant

Bolsen says another important silage management decision is the use of a lactic acid bacterial inoculant. He says research backs this practice. Bolsen added that applying an inoculant at the forage harvester should be a “no brainer” because it reduces DM loss in corn silage by 1.5 to 2 percentage points. To calculate the value of using an inoculant, Bolsen  referenced a dairy herd with an average production of 80 pounds of milk per cow per day, a ration DM intake of 53 pounds per cow per day (16 pounds of corn silage DM per cow per day), $22-per-hundredweight milk price and $65 per ton of silage. Reducing shrink loss with an inoculant, which he estimates costs approximately 2 to 3.5 cents per cow per day, increases net income by $60 to $75 per cow per year.

Regardless of the size of operation, Bolsen says this is “not a perfect world” and that mistakes leading to higher than optimum shrink losses can occur in every silage program. However, he says, working within “the silage triangle,” which includes the beef or dairy producer, the forage grower and the silage contractor, producers can fine-tune silage management practices, reduce silage DM lossesand reduce the cost of feeding a ton of silage.


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