Can the type of plastic you use to cover silage in a bunker reduce dry matter losses during storage?
Maybe, says Rich Muck, researcher at the U.S. Dairy Forage Research Center in Madison, WI.
Muck is wrapping up studies comparing a traditional, plastic-and-tires silage-covering system to a Silostop system recently introduced in the U.S. While stressing that results are preliminary, Muck says the new system shows some promise.
“From what we've seen so far, it clearly is a very good system if it's done right,” says Muck.
Developed in Europe, Silostop is an impermeable, plastic film 25-50% thinner than the plastic traditionally used for covering silos. Company literature claims ordinary plastic is porous, allowing oxygen to pass through. That's one reason dry matter losses in the top 3' of silage can be as high as 20%.
The company adds that the film creates an effective barrier to oxygen and can reduce losses to less than 5%.
In addition to covering the bunker with the film, Silostop recommends lining silo walls with it, using woven fabric tarps over the top to prevent bird and rodent damage, and using sandbags rather than tires to anchor covers.
Some of Muck's observations after using the system for three years:
Labor requirements aren't much different. “We didn't put a stopwatch to it,” he says. “But it seems to take less time to cover a bunker this way than with plastic and tires.”
The system reduces spoilage at the walls. “The only time we saw visible spoilage at the walls was when we failed to get a good seal between the sidewall and top sheets of film,” says Muck.
Putting plastic between silage and sidewalls can thwart corrosion that occurs when silage juices come into contact with concrete.
“If you have an aging bunker, you might be able to get a few more years of useful life out of it,” says Muck.
On the downside, lining walls with plastic might slow silage packing operations. “You have to be a little more careful to make sure you don't rip or tear the plastic with an axle or tire.”
Sandbags offer some advantages. “Sandbags take up less room in storage than tires,” says Muck. “They're also less likely to be a home for rodents and other vermin.”
Tarps need to be reused to keep the cost of the system down. “If you're in an area where you get snow, you'll probably want narrow tarps to reduce the amount of tarp you roll back as you feed out of the silo,” he says.
He estimates that the initial cost of a complete Silostop system — cover film, tarps and sandbags — is about double that of a traditional plastic-and-tire system.
“The question most producers will be asking is whether they'll be able to reduce dry matter losses enough compared to a traditional system to justify the added cost,” says the Wisconsin dairy researcher. “We hope to have estimates of losses from our trials summarized by summer.”