Ideal density
As a general rule of thumb, livestock specialists suggest producers strive for an average packing density of 15 pounds of dry matter (DM) per cubic foot or more.

“If possible, producers should get that number closer to 17 pounds per cubic foot and the higher the better,” says Matt Laubach, DuPont Pioneer dairy specialist.

“This helps improve efficiency in the overall fermentation process.”

By increasing DM density by another two pounds, producers potentially save another 1.5 percent DM by preventing oxygen penetration.

Dry matter loss is not fiber; it’s carbohydrates like sugar, so figuring the cost of the loss requires a producer to calculate the cost of replacing that 1.5 percent with an energy source such as cornmeal.

Many beef and dairy producers are not achieving the recommended minimum silage DM density. Producers should pack and cover silage to exclude air, which reduces fermentation loss.

Silage density and shrink loss are inversely related, so as packing density increases, shrink loss decreases. Therefore by improving density by two pounds, producers are able to reduce shrink loss by about 3 to 5 percentage points.

Packing it in
Silage should be applied in thin layers that do not exceed six inches and then compacted before the next layer is applied.

Studies have shown that 45 to 60 percent of wheeled tractor weight transferred to forage is lost when more than six inches of forage is packed at a time.

“The operator of the pack vehicle, just like in highway construction, is highly responsible for ideal compaction,” Laubach states.

The next important factor is the overall weight of the compaction equipment. The packing tractor should be as heavy as possible to achieve high forage density.

When packing, remember to use the rule of 800. It works like this: Multiply the number of tons coming in each hour by 800. That represents the total pounds of tractor weight needed for packing per hour. For example, if a producer is bringing in 250 tons per hour, that means 200,000 pounds of tractor weight is needed.


Improving density
First, producers should check silage densities but only if it can be done safely. Also, be prepared to adjust filling and packing procedures after this check.

Another option is to reduce the forage delivery rate. This is difficult to accomplish, as few producers and silage contractors are inclined to slow the harvest rate.

Employing well-trained, experienced people especially those who operate the push-up or blade tractor is a great benefit to producers who strive for optimal compaction.

Improving density also comes from increasing the rate of forage push-up and packing. By increasing this and the harvest rate, producers will reach the target density.

Measuring silage density
A silage density probe can be used to help customers determine packing densities of their silages. Assessing silage densities provides silage managers a report of how well they packed forage during silo filling, which is dependent on specific factors, such as tractor weight, packing time and packing strategies (e.g., not packing too much under the wheels).  

Safety practices should always be observed when approaching the silo face. It is essential to assure it’s safe to make a silage density assessment with the density probe each time the face is approached.

If the silo face is exceptionally high, displays overhangs or has a loose face, it is very important to stay away. In those cases, assessment of silage density can be determined by on-line calculators that determine the density by inputting the silo face dimensions and weight of silage removed on a daily basis.

So as producers begin the silage harvest and packing season, remember that packing is a science.  FG

PHOTOS
TOP: The packing tractor or dozer should be as heavy as possible to achieve high forage density.
BOTTOM: A silage density probe helps customers determine packing densities of silages. Photos courtesy of DuPont Pioneer.