Cut your silage losses in bunker silos


MADISON, Wis. – Forage is too valuable to be lost because bunker silos or silage piles are sized incorrectly or inadequately managed, says University of Wisconsin Extension agricultural engineer Brian Holmes.

He explains that each 10 percent loss of dry matter for hay silage represents about $1,940 a year for each 100 cows when fed a 50-50 ration of hay and corn silage.

Feedout rate. Dry matter loss occurs in silos because of inadequate feedout face removal rate, inadequate silage density, exposure to oxygen or rainwater and juice seepage.

Holmes says these losses can be avoided or minimized.

For example, adding a 100-foot long wall to create three bunker silos instead of two will add an initial cost of $7,500 when the wall costs $75 per foot

Using a 12 percent depreciation, interest, repairs, taxes, and insurance factor, the $7,500 initial cost is converted to an annual cost of $900 a year.

The result is a net profit of $1,040 for a 100-cow herd.

Less seepage. You can minimize seepage by harvesting at a moisture content of less than 70 percent and covering the forage to protect it from rain.

You can control density with the packing process, forage moisture content, packing tractor weight, delivery rate of forage from the field, and depth of forage.

High rates of delivery by use of modern self-propelled, high-capacity forage harvesters can result in low-density silage, which allows easy oxygen penetration into the exposed surfaces.

Plastic film. Eight mil plastic held close to the silage surface by a weighting material limits oxygen and rainfall exposure.

Some producers report improved forage quality along bunker walls when they line the walls with plastic film and placing the wall lining plastic under the top cover plastic at the joint.

The wall plastic excludes from the silage water running down the wall.

The wall plastic also keeps oxygen from penetrating through wall cracks into the silage.

Common mistake. The rate of feedout (inches per day removed from the face) is influenced by how much feed is needed each day and the area of the feedout face.

A common mistake is to design a horizontal silo so wide that the feedout rate is too low.

Wide bunker silos are less expensive than narrow silos because narrow bunker silos require more length of bunker wall for a given volume stored.

Producers can save silo wall cost by making bunker silos wide, but this can have a high annual cost due to higher dry matter loss as shown above.

Fact sheet. More detailed recommendation on the use of bunker silos is available in a recently revised publication, Managing and Designing Bunker and Trench Silos (AED-43).

You can get this publication from or by calling 515-294-4337.

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Get the details

* Managing and Designing Bunker and Trench Silos


* University of Wisconsin Extension Team

Forage Harvest and Storage Web page


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