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 3 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 feet. A 30 percent loss in this 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 a 2 percent loss on the entire pile, an additional loss in this example would be 53.8 tons of silage worth another $2,690.
Technology is bringing more environmentally and user-friendly silage-covering products to the market each year, yet polyethylene (for example, 6-mil plastic) still remains one of the most cost-effective materials for covering silage.
After it is placed over ensiled forage, the plastic sheet must be weighted down. Tires are 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.
The cost of plastic is in the range of $0.115 to $0.120 per square foot, so covering an 80- by 140-foot bunker silo with concrete sides (includes a 5 percent overlap) would cost about $1,344. If we assume that covering the forage takes about 25 man-hours of labor to roll 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, when all the calculations are made in this example, the total value of silage saved is far greater than the total cost of covering, providing about a 7.6-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.
Editor's note: This was originally written for dairy producers, and has been edited to fit beef producers.