General perceptions about forage grasses may very well be wrong, according to University of Wisconsin Extension and Forage Agronomist Dr. Dan Undersander.

Many dairy producers and nutritionists believe that forage grasses are too high in fiber and too low in quality for high-producing cows, but Undersander and others who have studied forage grasses found the digestibility of neutral-detergent fiber (NDF) in grass is more digestible than the NDF in alfalfa. Plus, there are many agronomic advantages to growing a grass-legume mix.

Undersander says, “Initial feeding trials we have run have indicated that we could maintain high levels of milk production when replacing a portion of the corn silage and alfalfa with grass silage, even though dietary NDF increased slightly.”

He continues, “The perception is that forage grasses are too high in fiber. Pure alfalfa stands do produce top-quality forage, but grass fiber managed properly in an alfalfa-grass mixture can be more digestible than alfalfa.”

While corn silage forms the base for many high-quality diets for dairy cows, its high starch and low fiber make-up can be pushed too hard in diets, leading to rumen acidosis and increased lameness in dairy cattle. Use of a grass and alfalfa mixture also has the potential to reduce non-fibrous carbohydrate (NFC) in dairy rations. Grass runs about 15 percent NFC, while alfalfa is about 25 percent NFC, and corn silage is about 35 percent. As Undersander says, “A little grass could be a good thing.”

Undersander’s work indicates dairy producers could maintain high levels of milk production when replacing a portion of the corn silage and alfalfa with alfalfa-grass forage.

Some of the advantages of incorporating some grass into alfalfa stands include:

• Increased yield of seeding-year stands; some grasses, such as Italian ryegrass, will establish faster than the alfalfa and produce more total forage yield in seeding year than alfalfa alone.
• Possible higher yield in production years
• Cut hay that is 30 to 40 percent grass mixed with alfalfa will dry faster than pure alfalfa or even pure grass stands.
• A wider harvest window on second and later cuttings because many cool-season grasses will not head out much after first cutting. Re-growth is primarily leaves which change little in forage quality during the seven to 10 days around harvest time.
• Grass has higher tolerance against winterkill, heaving, standing water, wheel traffic and cattle traffic. (But beware; some varieties of orchardgrass and tall fescue are not as winter hardy as others and will die before alfalfa.)
• Possible longer life of the stand, especially if considering this option to keep marginal land in forage longer.
• More tolerance of manure application and better use of nitrogen in the manure.
• Stands with grass are less attractive to potato leafhoppers.

So why isn’t everyone doing this? Disadvantages include fewer weed management options, the ratio of grass to legume in the mixture can change over time, and there is a learning curve for farmers in selecting top grass varieties for this purpose.

“However, establishment, cutting schedule and harvest management is about the same as with pure alfalfa,” Undersander says.

Undersander emphasizes the “key to managing alfalfa-grass mixtures for high-quality forage is to maintain forage stands that contain about one-third grass and two-thirds alfalfa.”

Different situations call for different grass species. Undersander’s research suggests the best grass species for this purpose include orchardgrass, tall fescue and meadow fescue. Within these species, he recommends selecting those varieties rated near the top in yield, winter hardiness, maturity (it is best to have late-maturing grasses so the grass is close to heading out when alfalfa is ready to harvest), consistent yield throughout season and rust resistance.

When purchasing grass seed, Undersander urges producers, “Never buy ‘variety not stated.’ Variety selection for a grass forage is just as important as hybrid selection for corn silage. Take time to study variety trials and talk to seed dealers that understand grass varieties.”

He notes, “It is important to recognize that more plants emerge than contribute to the final stand. In fact, the biology is that many plants germinate and begin growing; then the stand thins to what can be maintained by the soil and environment. We have found, for example, with pure alfalfa, no matter how many pounds of seed are used per acre, the stand will thin to 30 to 35 plants per square foot by summer’s end.”

His study shows the same principle applies to grasses: At higher seeding rates more plants emerge, but then greater thinning occurs as the season progresses. However, the fescues did not thin as rapidly as the alfalfa and the percentage of grass plants tended to increase as the season progressed. Orchardgrass has lower germination and declined at about the same rate as alfalfa so the alfalfa-grass percentage remained about the same as the season progressed.

Undersander’s recommendation is to seed at moderate rates. He says to obtain the ideal 30 to 40 percent grass in an alfalfa-grass field to plant per acre:

• 10 pounds alfalfa: 2 to 4 pounds of orchardgrass
• 10 pounds alfalfa: 6 to 8 pounds of tall fescue
• 10 pounds alfalfa: 6 to 8 pounds of meadow fescue

Although different species and varieties will produce more at different times of the growing season (i.e., timothy and smooth brome grass produce heavily in the spring but less later on), Undersander says the grass varieties chosen will generally have very little impact on the total season’s yield.PD

Kelli Kaderly-Boylen is a freelance writer based in Iowa.

To learn more about this topic, go to the University of Wisconsin Forage Resources website or read a related article, "How about including some grass in that new alfalfa seeding?" from our sister publication, Progressive Forage Grower.

PHOTO
Producers chop alfalfa-grass mixtures in Pennsylvania for haylage with higher digestibility than pure alfalfa. Photo by PD staff.