Grasses are gaining ground on Wisconsin dairy operations, both
for grazing by the cows and mechanical harvest. Grasses bring in
highly digestible fiber and improve cow performance and
U.S. Dairy Forage Research Center agronomist Geoffrey Brink
explores reasons for feeding grasses, agronomics and some
differences between grasses and alfalfa (the forage with which most
producers tend to be more familiar). He also looks at some grazing
issues (in a companion article this week).
More producers are intentionally establishing grass as high quality
forage for their confinement dairy rations. Not only do grasses
look good in terms of NDFD, but they make a positive impact on milk
fat. With today’s high-producing cows fed considerable grain,
producers must be extra cautious about feeding adequate fiber. A
grass/legume TMR has more total fiber than alfalfa alone in the
TMR. Grass, as noted, has a higher proportion of digestible fiber
than either alfalfa or corn silage, and it’s an especially good fit
with corn silage (which is lower in fiber and high in non-fiber
Brink notes that grasses at boot run 70 percent NDFD versus
comparable-quality alfalfa more like 50 percent NDFD. And while
alfalfa is about 35 percent NDF, grasses come in around 55 to 60
However, because grasses bring more fiber to the ration, they also
slow passage of feed through the cow, notes Brink. “If all other
ration components remain the same, this will also reduce intake,”
he cautions, citing research showing grass-based diets having
little negative effect, though, on animals with lower nutritional
demands, like late-lactation cows, dry cows and heifers. Producers
should be aware that adding grass can reduce milk output when cows
are at peak lactation, because of that reduction in intake.
In terms of agronomics, grasses have fewer problems with pests and
winterkill than alfalfa. They dry faster than alfalfa, too. They’re
highly responsive to nitrogen, and provide one more place to go
with manure application.
That is, in fact, one of the biggest advantages of growing grasses
on a dairy farm, according to Brink. With a grass forage crop,
manure can be applied early spring and after each harvest all
summer long, and the grass will return the favor, too, with higher
yield. Further, this USDA agronomist notes that “because of the
year-round vegetation and fibrous root system of grasses, there is
less potential for nitrate leaching than with corn.”
Brink says grass seed/varieties should be chosen with as much care
as alfalfa and corn. Don’t just plant whatever’s in stock. Go with
a named variety, as opposed to “variety not stated” on the label.
Pick medium to late-maturity varieties for maximum harvest
flexibility. Also consider rust resistance to avoid forage
quality/palatability problems. He directs growers to the University
of Wisconsin’s “team forage” website
(www.uwex.edu/ces/crops/teamforage/ and then select UW Forage
Resources and then “grasses”), or Cornell University’s “Forage
Species Selector” at www.forages.org.
Popular picks for confinement rations are monocultures of smooth
brome, tall fescue and orchardgrass. Meadow fescue, real popular
with the graziers, can also be appropriate for mechanical harvest,
but recognize that you may be giving up some yield for meadow
fescue’s added nutritional value, says Brink.
More persistent grass can be sown with less persistent grass for
faster cover and improved seeding-year yield, Brink advises. For
instance, seed tall fescue or orchardgrass at 10 pounds to the acre
with Italian ryegrass or Festulolium at two pounds, April to May or
July to August. Apply 30 to 40 pounds of nitrogen per acre when the
seeding hits 4 to 6 inches. Control broadleaf weeds with herbicide
and annual grass weeds by frequent clipping in the establishment
year, Brink suggests.
Producers used to alfalfa fixing its own nitrogen may overlook that
grasses “need some help” via fertilizer or manure. Applications
early spring-before and after first harvest-have the greatest
impact on yield due to seasonal growth patterns. Brink cites
research showing annual yield of grass continues to climb as more
and more nitrogen is applied (from 1 to 300 pounds). However, the
“efficiency of yield production”-or pounds of dry matter produced
per pound of N added-declines after the annual N rate gets over 120
to 150 pounds.
Whether the N source is fertilizer or manure, Brink recommends
split application-with no more than 60 pounds of N per acre each
time-to improve the “utilization efficiency by the crop and the
cows. Excess nitrogen fertilizer leads to more protein in the crop
and consequently more nitrogen excrete in the manure,” he
One thing to be aware of is potassium levels. Brink says a high
potassium concentration in grasses can cause problems with cows
after freshening. To reduce the risk of milk fever, stop feeding
high-potassium grasses three weeks prior to calving. Orchardgrass
and perennial ryegrass have the highest potassium levels.
Ways to manage grasses for reducing potassium concentration
include: Growing them on low to medium-potassium soils; feeding
first cutting to heifers and dry cows (as potassium levels are
highest in the spring) and applying manure in summer or fall when
potassium content of the grass is lower.
Brink notes that harvest timing is a major consideration in the
spring with grass, as quality is higher than alfalfa’s in the
spring, but also declines more rapidly compared to alfalfa-and also
when compared to subsequent grass cuttings (when the quality is
lower but declines more slowly). Thus timing of first cutting is
more critical whereas that of summer and fall cuttings can be
delayed some if necessary.
Brink tells Agri-View that cutting height is also a major
consideration. While a closer cut means higher yield, it will
impact stand persistence. He says producers harvest alfalfa leaving
1 to 2 inches of stubble, but that’s very hard on grass. He
recommends leaving at least three inches, with four inches even
better. Cutting grass too short leaves the crop no reserves for
recovery from photosynthesis. Grass would much rather begin
regrowth from photosynthesis of existing leaves than from export of
carbohydrates from stem bases.
The other harvest consideration is that grass dries faster than
alfalfa, so monitor moisture, notes Brink. Adequate packing is also
critical for “good grass silage,” he says, mentioning that when
both alfalfa silage and grass silage are at the same moisture, the
grass silage’s density will be slightly less. A common mistake is
to not pack it well enough.
Grasses should be put up at 60 to 65 percent moisture for a bag,
bunker or pile, and between 50 to 60 percent for tower silos. If
you’re making wrapped bale silage, moisture should be under 60
The bottom line is that every producer needs to decide whether
grass fits into their system. If it’s a go, then manage that grass
as carefully as you would alfalfa, Brink says.