Adding a small amount of grass to high-quality corn silage and alfalfa dairy rations could tone down energy levels while boosting fiber, says Dave Combs, University of Wisconsin dairy scientist. That may reduce the amount of laminitis in dairy cows currently being fed hot diets.
“We’re burning these cows up," Combs told the crowd at last month’s World Dairy Expo. “Survey results show 20-25% of all cows in the Upper Midwest are mildly lame. That’s a scary number. About 42% of the lameness cases that veterinarians have identified are basically due to nutrition. The laminitis issues we’re seeing on farms are directly related to feeding diets that are too hot.”
With today’s high-quality corn silage and alfalfa, it’s often not feasible to cool hot rations by removing corn silage and incorporating more alfalfa, he says. “In many situations, there is a need for highly digestible fiber, and grasses would seem to be a more effective source of fiber than a high-quality (>160 RFQ) alfalfa.”
He suggests seeding grasses like reed canarygrass, perennial ryegrass, tall fescue, annual ryegrass or orchardgrass with alfalfa. “If they’re well-managed, grasses are an excellent source of protein for dairy cattle – around 20%, just like our alfalfas. They’re actually a little higher in fiber and that’s not necessarily a bad thing. A lot of the rations I see in the Midwest are incorporating straw into the diets to pull enough fiber into them. Why not pull a source of fiber that’s got some digestibility and some energy in with it?
“The proportion of fiber that’s digestible is actually higher in grasses than it is in alfalfa and corn silage,” Combs continues. “So every mouthful of fiber that cows get from grass has some energy value.”
Mixing grasses with alfalfa in a growing system has other benefits, he says. “You get some faster drying … and grasses incorporated with alfalfas do reduce risks of winterkill.” Grasses also bulk up establishment-year yields of alfalfa and aid in manure management. “Grasses suck up manure nitrogen,” Combs says.
“I’m not talking about taking alfalfa completely out of the ration,” he cautions. “I’m talking about putting a small amount of grasses in combination with corn silage and alfalfa in the diet. To make these diets work, though, they have to be high-quality grasses.”
One problem, he says, is that there’s been little research in how to strategically use grasses in modern dairy diets. “There is a need to evaluate the potential of grasses with legumes on high-corn-silage diets that are low in fiber and high in NFC,” Combs concludes.