Most forages grown to replace winterkilled alfalfa in the Upper Midwest this year are good enough for milk cows. Some may even work in high-cow rations, says Randy Shaver, University of Wisconsin extension dairy nutritionist.
“Maybe you'll have to spend a little more time and effort in feed testing and ration balancing,” he says. “But sometimes people are amazed at what they can achieve with these alternative crops.”
A good forage test is the key, adds Marcia Endres, University of Minnesota dairy nutritionist.
“Feeding these forages will require an analysis because they're so different,” she says. “They'll vary, depending on when you planted and when you harvested.”
Variability is especially high for forage mixtures because they contain differing amounts of each crop, she says.
A conventional NIR forage test may not be good enough for emergency forages, says Endres, and Shaver agrees.
“We don't have a good NIR database on emergency forages, so I would certainly recommend that they be analyzed with wet chemistry,” he says.
The analysis should include an NDF digestibility test. Certain emergency forages may be high in indigestible fiber, which would limit the amount that can be mixed into a milking ration.
“You might have to include some digestible-fiber byproducts, like soy hulls, to balance that,” says Endres.
Among this year's popular alternative silage crops, small grains and small grain-pea mixtures have the highest potential quality, says Shaver. If the small grain was harvested before dough stage, the forage can be as nutritious as alfalfa haylage. After the grain crop heads out, though, it has more fiber and less energy and protein.
Soybean silage feeds a lot like alfalfa haylage, too, he says. It has a bit less energy, but is high in protein, calcium and potassium.
“You have to be careful on straight soybean silage for dry cows, just because of its very high potassium and calcium content,” he says.
Forage sorghum and sorghum-sudangrass are low in protein but fairly high in energy. Brown midrib varieties are comparable to corn silage, but conventional varieties have a little less energy, says Endres.
Mixtures of soybeans and sorghum or sorghum-sudangrass should be fairly high in both protein and energy. But the analysis will vary according to the amount of each crop in the mix.
Before feeding begins, examine the silage to make sure it fermented properly, Shaver recommends. However, if the alternative crop was harvested at the right moisture content and was chopped and packed properly, fermentation shouldn't be a problem.
“The one that can be a bit of a challenge is straight soybean silage,” he says. “It might not have enough fermentable substrate relative to protein. Some people blend it with corn silage to get better fermentation.”