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Dairy Focus: Is Covering Silage Worth the Cost?

J.W. Schroeder, NDSU Extension dairy specialist (NDSU photo) J.W. Schroeder, NDSU Extension dairy specialist (NDSU photo)
Keeping silage from spoiling is a cost-effective effort.

By J.W. Schroeder, Dairy Specialist

NDSU Extension Service

Dairy producers have been putting haylage into bunkers, bags and piles for nearly two months, and ensiling corn is but a couple of months away. This is a reminder that despite the work, covering silage is cost-effective.

When silage is not tightly covered, air and moisture can enter the silo easily and adversely affect the ensiling process and the quality of silage during storing and feeding. This creates a great potential for excessive dry-matter (DM) and nutrient losses, moldy feed and other problems.

The extent of these losses in the top 2 to 4 feet is far greater than most people realize. Several studies at Kansas State University reported at least a 30 to 40 percent loss in DM from the top 3 feet of silage in uncovered bunker silos, compared with bunkers covered with plastic sheeting weighted down with tires.

In a 12-foot-high by 80-foot-wide by 140-foot-long bunker, the top 3 feet of silage contains approximately 672 tons (as-fed) of silage at a density of 40 pounds per cubic foot. A 30 percent loss in the original top 3 feet would equal 201.6 tons of as-fed silage. If this is corn silage, for example, and it is worth $50 per ton as-fed, the total loss would be at least $10,080.

This does not take into account any negative effects that the top 3 feet of spoiled material might have on DM intake, milk production or reproduction. Nor does it consider that additional silage is lost on the sides and closed end of uncovered bunkers. These added losses easily can amount to 2 to 3 percent of the total silage volume. Assuming an 8 percent shrink loss for all silage below the top 3 feet of the bunker is realistic, the additional loss in this example would be 193.8 tons of silage worth another $9,650.

The cost of 6-mil plastic to cover the bunker is in the range of 4 to 5 cents per square foot, so covering an 80- by 140-foot bunker silo with concrete sides (includes a 5 percent overlap) would cost about $1,200. The shrink loss in the original top 3 feet would be about 17.5 percent (range 15 to 25 percent), which is equal to 117.6 tons of silage worth $5,880. This compares to silage worth $10,080 lost with no cover. Now that should get your attention!

Technology is bringing more effective and more environmentally and user-friendly silage-covering products to the market, which will make the longtime standard (6-mil plastic) no longer your most cost-effective choice.

After any cover is placed over ensiled forage, it must be weighted down. Tires remain the most commonly used weights. They should be placed close together so they touch (about 20 to 25 tires per 100 square feet). To reduce the number of tires needed and prevent water from pooling inside the tires, they should be cut in half and placed with the open side down.

If we assume that covering the forage takes about 25 man-hours of labor to roll the film, add the plastic and throw the tires at $12 per hour, the total labor is $300 for this pile for the year. The initial cost of tires to cover this silo would be about $250 to $500. If we assume an initial tire cost of $350, with the tires having a 10-year expected useful life, this amounts to $35 per year.

Your decision is not if you should cover but what covering you should choose. While that discussion is not covered here, the total value of silage saved is far greater than the total cost of covering, providing about a 3- or 4-to-1 return on your investment (before the cost of disposal of the used plastic). These results are similar to those reported by Kansas State University researchers. Plus, you have the added benefit that your valuable animals are not exposed to the potential toxins in the spoiled silage.

I remember my dad lamenting the cost and time to put up silage, but in the same breath, he reminded me that silage was sure good feed to make milk. Through the years, we have accepted waste as a part of doing business. However, the dramatic increase in the costs of growing and harvesting feed and forage has reduced profit margins. Reducing spoiled silage waste is one very effective cost-reducing decision.

And while new methods and materials are on the way, employing almost any technology that reduces waste and maintains feed quality is a sound and logical enterprise decision. The bottom line is that sealing the exposed surface is one of the most cost-effective management decisions in any silage program.

NDSU Agriculture Communication - July 16, 2015

Source:J.W. Schroder, (701) 231-7663,
Editor:Ellen Crawford, (701) 231-5391,
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