Grazing dairy farmers are constantly thinking about forages and nutrition. Planning for the grazing season means optimizing spring forages, finding ways of coping with the summer slump and strategizing for autumn.
Improving forages and forage utilization by enhancing quality and quantity of available pasture forages and increasing cow intake of digestible forages requires an understanding of dairy cow nutrition needs and forage characteristics.
Making the most milk from forages requires harvesting the plant at the right time, whether the cows do it themselves or it’s cut for baleage or silage. Both grazing management and feeding strategy matter. The quality and quantity of pasture is important, as the primary limiting factor in grazing dairy herds is energy. Overgrazed pastures are detrimental to soil, plant and animal health.
Fed rations need to account for the changing digestibility and nutrient content of pasture. But fed rations, whether purchased off-farm or grown, harvested and stored on the farm, come with a monetary cost. Knowing how to weigh gains in milk production and resulting income against the price of feed ingredients is important.
Milk From Forages
“Getting cows to milk off pasture – there’s a high level of management that it tends to take,” Larry Tranel, Iowa State University dairy field specialist, said on a recent episode of the Dairy News and Views podcast.
Forages are becoming even more important, particularly in organic dairy herds, as certified organic feeds have become too expensive for many farmers to purchase. The University of Minnesota’s dairy herd is split into both a conventional and an organic herd. The organic herd isn’t getting the soybean meal that they used to receive to supplement grazing.
“It just isn’t cost effective. Feed costs are still really high. It just doesn’t pencil out,” said Brad Heins, associate professor of organic dairy management at the University of Minnesota’s West Central Research and Outreach Center in a recent episode of the Moos Room Podcast. “How do we improve our forages so we don’t have to feed expensive feed?”
Planning for the grazing season has to start well before cows are turned out to spring pasture. The time to think about “what your forage is going to be like this spring, summer and even into fall, and to have a plan,” is prior to the snow melting, Heins said.
For many dairy farms, alfalfa is a staple. Heins encouraged farmers to consider adding grass to pure alfalfa stands. The digestible fiber is the most important quality when considering forage nutrition, he said – “It comes down to calculating the tonnage of digestible fiber in the ration that you have.”
One acre of alfalfa, with a yield of 3.5 tons/acre, will result in 1,260 pounds of digestible fiber. If four pounds of grass, such as meadow fescue or orchardgrass, are added to this ration, the digestible fiber is increased to 1,900 lbs./acre, Heins said. Adding in Italian ryegrass, at 8 lbs./acre will increase fiber digestibility even more.
No-tilling grass into a thinning alfalfa stand early in spring can give you another year before renovating that field, Heins said. “You’ll get a lot of good forage, especially in early spring, and then the late fall.”
The biggest factor limiting dairy cows on pasture is the 27,000 bites per day maximum that they can take, Tranel said. In confinement, a dairy cow can receive all of its daily dry matter intake in 11,000 bites. Those bites occur in 3.5 hours. On pasture, there is slower rumen passage. Higher protein levels in forages means that the kidneys need to work too, to excrete excess protein in urea, thereby increasing the amount of energy used in digestion.
Sward density is the key to producing quality and quantity of grass. If high producing dairy cows are left on spring pasture too long, the pasture will begin to regrow and the cows will eat that regrowth. It takes a lot of bites to get this regrowth. So not only will grazing this regrowth limit future pasture productivity by weakening the plant, it will also limit milk production.
“For milk cows, we tend to say you take about half of it. You get it down to about to six or eight inches, and that’s about as far as you want to go with a milk cow. Because then you are going to be sacrificing milk production,” Tranel said.
Managing the grazing period and moving the cows on and off pasture quickly, and when the pasture is in its vegetative state and tall, is important. For dairy herds, only grazing half the height of the forage is recommended. Moving the milk cows at least every 12 hours in spring is recommended.
It takes a while for grass to regrow to four inches tall, but then it grows quickly while in the vegetative state. Avoid letting the pasture go to seed when grazing. In spring, rest periods for pasture might only be two weeks. But in summer and autumn, that rest period will change with plant growth rates, Tranel said.
Seeding legumes into grass will fix nitrogen and maximize grass growth. Using multi-species crop mixtures – sunflower, sorghum, buckwheat, clovers and more – can be another route to enhancing soil health and creating high-quality forages.
“Forages tend to grow better together. Anytime you put another grass into that monoculture you can actually increase its yield by 15% to 20%,” Tranel said. “Sward density is so important, because when that cow takes a bite, she better be taking a darn big bite.”
Palatability matters, and it can differ even within species. If a cow can’t intake enough forage, either production will be sacrificed or a feed supplement will be needed. When pasture forages are meeting the cows’ needs, such as with lush spring pastures, they will reduce any grain supplement intake on their own.
“The cows will come in the barn and they’ll see the grain, and they won’t even clean up their grain because they like their pastures so well,” Tranel said.
Economically, there is a lot to think about when deciding whether to feed supplemental grains or not. When you feed a pound of grain to grazing cows, you are not displacing a pound of forage, but roughly half of a pound of forage, Tranel said. That pound of grain will result in an increase of about two-thirds of a pound of milk. Depending on the price of that pound of grain, it may not be economical to feed it, even with the added milk.
Extending the grazing season is another way to maximize forages from your land, Heins said. Maximizing the digestible fiber per acre of land is the goal. Grazing cover crops, incorporating native warm season grasses that grow in the heat of summer or incorporating winter rye into a corn rotation are all possible ways to increase forage availability. Sorghum, which is highly digestible, can be harvested for silage at eight to 10 feet tall, and it can be harvested following a frost. Sorghum can also be grazed.
“There’s definitely a lot of different ways to feed these cows,” Tranel said.
by Tamara Scully