Custom harvesters should know at what percent moisture their clients want their alfalfa chopped and packed. That will give them happy repeat customers with healthy cows, says Bill Kautz, a forage and nutrition specialist with Chr. Hansen Biosystems, Milwaukee, WI.
“They certainly need to know that we are trying to avoid that 70% moisture level. And we're trying to stay wet enough so we don't have spoilage problems in terms of yeast growth when feed out starts,” says Kautz.
Dairymen have complained to him of low-quality silage that they think was put up too fast by custom harvesters, with little attention to moisture content.
In Arizona, in fact, custom operators have put direct-cut alfalfa into bunkers. “They're just going to have to plan their business around getting the right percent moisture. It's not fair to producers to have problems for custom operators' convenience,” Kautz says.
He recommends a moisture-level range of 60-68%, aiming for the high end of that range for bunker silos. “If you go above 40% dry matter in a bunker you're going to have to chop finer or add more weight to your pack tractor,” he adds.
On the other hand, if alfalfa silage is too wet, anaerobic bacteria called clostridia grow in it. Clostridia cause dry matter and energy loss and are harmful to transition cows.
“The problem is, it's sort of like a haircut; once it's done, you can't undo it,” says Kautz of alfalfa chopped too wet or dry. “Once it's in that bunker or silo, you have to live with it. That's why it's important to have an understanding between dairymen and operators on moisture levels.”
Along with moisture levels, custom operators who pack bunkers need to know just how tight — or loose — they're doing it.
“As in corn silage, we would like to see a haylage density of 15 lbs/cu ft on a dry matter basis,” says Kautz.
Research has shown that at least 800 hour-pounds of weight are needed per ton of silage for sufficient packing. To determine bunker density, an operator should know how much his pack tractor weighs. Then divide the weight by 800 hour-pounds and that equals the rate of fill.
“Say you've got a 32,000-lb tractor. You divide by 800 and that's 40. It means you can only bring in 40 tons/hour to get the bunker adequately packed.
“A lot of custom guys tell me, ‘But we're bringing in 100 tons now!’ I say, ‘Well, if you're bringing in 100 tons, you need 80,000 lbs. So you need two four-wheel-drive tractors and you need to spread the layers out thin’,” adds Kautz.
To calculate bunker silo density, based on tractor weight and the depth of silage layers, download the “Bunker Silo Density Calculator,” an Excel spreadsheet by Brian Holmes, Wisconsin extension engineer, and Richard Muck, U.S. Dairy Forage Research Center ag engineer. You can find the download at: www.uwex.edu/ces/crops/uwfor age/dec_soft.htm.