Can Grass Forages Work in Dairy Diets?

 

Could a little grass in your ration be a good thing?

 

Grasses have been replaced by corn silage and high quality alfalfa in Midwest rations, but Dr. David Combs, Department of Dairy Science, University of Wisconsin–Madison said there may be a place for them in the diet again.

 

“I’m not going to talk about replacing high quality alfalfa or corn silage,” Combs said at the Vita Plus Dairy Summit today in Green Bay, Wis. “Grasses can be a commodity feed that fits in rations like soy hulls. It gives us some flexibility.”

 

Grasses have been known to have some challenges. They are higher in fiber and if not managed correctly can lead to problems. When looking for maximum yields per acre, grasses don’t come close to corn silage. Pure alfalfa stands are easier to manage, but if you select the right grasses that mature late and are cut early there can be benefits.

 

"You’ve got to manage grasses just like you do everything else to make them work," he said.

 

Annual grasses can serve as cover crops to boost yields in the first year of a three- or four-year alfalfa rotation. Grasses aid in faster and more consistent drydown, can help to manage winterkill, and provide additional manure management options.

 

On the nutrition side, grasses have a higher proportion of digestible fiber. Producers are using wheat straw to gain rumen scratch, but that’s undigestible fiber. Unlike straw, grasses will also provide energy.

 

Work by University of Wisconsin Forage Specialist Dan Undersander in using ryegrass as a cover crop established that planting two to four pounds of grass yielded an additional 1/2 to 1 ton per acre of dry matter. Undersander also found that when planting at rates higher than four pounds per acre, the grasses challenge the alfalfa seedlings.

 

Perennial grasses, like orchardgrass, can add a substantial increase of neutral detergent fiber (NDF) to the forage yield. However, if you delay harvest by a week or two the fiber really starts to increase. Late maturity grasses should be planted and then they should be harvested early.

 

Alfalfa grass mixtures must be managed carefully, Combs said. “The timing of first cutting is very important. There is a lot of variability in terms of maturity in grass varieties and I’d rather cut the stuff in the vegetative stage than when it’s headed out.”

 

Grasses can be a good fit in high corn silage diets that are high in non-fiber carbohydrates (NFC) and low in NDF.

 

“Lameness is one issue we see a lot more of today than we did 10 to 15 years ago,” Combs said. “A lot of it is diet driven.”

 

Lameness is caused by a lot of different things, including low fiber diets, more than 40 percent NFC in the ration, sorting and slug feeding. "That’s why we’re adding wheat straw to high corn silage diets,” he said.

 

“If I’m going to reduce acidosis or manage lameness I need to watch what’s going on in rumen,” said Combs. Protein and NFC should contribute 75 percent to the total organic matter fermented in the rumen and NDF should be at 20 percent.

 

In a recent study, Combs compared a “smoking hot” corn ration with a treatment ration where one-third of the alfalfa was replaced with rye silage. Milk production stayed up and he witnessed a significant increase in fat test and a 3.5-pound increase in fat-corrected milk with the grass ration. In addition, no lameness was detected, but Combs also attributed that to new facilities with no overcrowding.

 

He mentioned more studies are needed, but considering the addition of grasses into the ration is going in the right direction thus far.

 

Combs recommended using tall fescue and orchardgrass because the new varieties of those grasses are standing head and shoulders above the rest. Brome and timothy grasses largely fall off the table because they don’t yield like the newer varieties. Italian and perennial ryegrass can really eat up manure and make for good annual cover crops.

 

The website – www.uwex.edu/ces/forage/resdata/grass_table.htm – can help with selecting grass varieties for fields in the Midwest. Producers should use yield, persistence, late maturity and establishment as their top criteria in choosing the grasses to plant.

 

The ideal stand will be planted at 20 to 30 percent grass to balance out alfalfa. That will leave enough legumes to fix the nitrogen for grasses to grow. If more grasses are planted, additional nitrogen may be needed.