Getting rid of the plastic and tires used to cover a bunker silo or silage pile causes big-time headaches on many livestock farms.

University of Illinois animal science researcher Larry Berger believes his edible silo cover may be the remedy.

“With an edible cover, you provide weather protection for the silage and also supplement the nutritive value,” he says. “It's an environmentally friendly alternative to plastic and tires.”

Berger started working on the edible cover concept about seven years ago. First step was finding a suitable material. He experimented with nearly 40 compounds before finally settling on a starch (wheat) and salt mixture. With a patent pending, he's reluctant to release details on other ingredients in the mixture. When mixed with water, it yields a substance that Berger compares to kids' playdough.

Early research results were promising. In one trial with alfalfa haylage, dry matter losses in a bunker with Berger's edible cover were 17% lower than in an uncovered bunker and nearly 3% lower than in a bunker with a traditional plastic-and-tires cover. All the silos were opened 106 days after ensiling.

Berger also notes that, when the cover material was fed to beef heifers at 2.5% of the ration, no sorting was observed.

Finding an efficient way to apply the covering has proved to be a trickier proposition than selecting ingredients. In the early going, Berger used a cement trowel to apply the starch-salt mixture. Thickness was ¾”.

After letting the cover cure for three days, he used a paint roller to apply a thin layer of molten paraffin wax over it. The wax seals the silo.

“Doing it that way worked just fine,” says Berger. “But it was way too labor intensive to be practical in a commercial livestock operation.”

Next, he tried using a cement pump powered by tractor hydraulics to mix the material. He applied it with an air compressor connected by hose to the cement pump. After allowing the cover to cure overnight, he applied the paraffin wax with a paint roller.

That method reduced labor requirements. “It took two people compared to the four or five people you'd need to cover a bunker with plastic and tires,” he says.

Even so, Berger sees one downside to that application method.

“A lot of farmers aren't likely to have all the equipment they'll need (like the cement pump) on hand. That would add to the expense.”

That led Berger back to the drawing board. He's putting the finishing touches on the design for a new application method that will make use of the packing tractor. The starch-salt mixture will be dumped into a feed mixing wagon or truck, mixed with water and then delivered to an applicator mounted on the rear of the tractor. As the packing tractor moves over the silage, the playdough will be spread onto it in swaths.

The applicator will also be set up with a roller that will lay a thick wax paper directly on top of the playdough. The paper will replace the paraffin wax. A press wheel on the applicator will smooth out the cover as the tractor moves over the pile.

“It will basically be a one-pass, user-friendly operation,” Berger explains.

He estimates the edible cover will cost around 18-20¢/sq. ft. That compares to 10-12¢/sq. ft. for a plastic-and-tires covering.

“But with the edible cover, you can replace some starch and salt in the ration,” Berger notes. “When you factor that in, the cost becomes very competitive with plastic and tires.”

He expects to have a prototype of the applicator ready for use this fall, and figures a commercial version of the edible silo cover and application equipment could reach the marketplace in two to three years.

“It's taken awhile to get it to this point,” he says. “But once we have it so that it's user-friendly and cost-effective, I don't think we'll have any trouble selling the concept.”