Some of these forages can also be beneficial in a fall or winter grazing program.
Mary Beth Hall (research animal scientist) and Geoffrey Brink (research agronomist) at the USDA-Agricultural Research Service, U.S. Dairy Forage Research Center in Madison, Wisconsin, both work with forages and nutrient needs of livestock.
“When we discuss energy-dense, we mean a forage that is more digestible, delivering more nutrients to the animal during a day’s worth of feed or grazing,” explains Hall.
Some feeds are very high in energy with a lot of non-fiber carbohydrates, and the fiber is very digestible, but if there isn’t sufficient quality, you still won’t meet animals’ needs. “We have to find a balance,” she says.
There are other plants that have a high level of structural carbohydrates but are not as palatable. “You need plants of high enough quality and quantity that the animals will eat enough of it. This goes beyond plant composition; it includes how you manage the pastures,” she says.
A number of forage species fit nicely into forage beef production programs, supplying adequate nutrition for growing animals or even finishing animals.
Brink says that in the South, the most popular option is overseeding a warm-season grass (like bermudagrass) with an annual grass such as annual ryegrass, which is very high-quality, low-fiber and highly digestible.
“In cooler climates, however, we rely on temperate or cool-season grasses that are perennial rather than annual, though there are some annual options. Wayne Coblentz, another one of the center’s scientists, has investigated oats planted in late summer to provide fall grazing."
"This gives a very high NSC feed from early September until snow falls, depending on when it is planted,” Brinks says. This could fill the gap in late fall when other grasses have dropped in nutrient quality and productivity.
“Stockpiled tall fescue is also good fall feed for beef cattle if adequately fertilized. The new endophyte-free varieties are a better option than the typical endophyte-infected Kentucky 31. For spring grazing, some people plant a mixture of turnips and wheat in the fall to provide some high-quality fall and early spring grazing,” he says.
Hall says most stockmen try to have a variety of forages to provide high-quality feed at various times of the year with no gaps.
“It depends on the growing season, however. There is no such thing as a foolproof crop. You examine the options that work in your own climate for filling in the gaps,” she says.
Legumes are another type of energy-dense forages often included in a pasture mix, particularly in perennial pastures. “Some people overseed perennial or annual legumes,” says Brink. “In the South, annual legumes such as crimson clover are often used. In a temperate climate, red and white clover and alfalfa are utilized, which are all perennial legumes. Legumes improve digestibility and energy content of perennial pasture significantly,” he says.
“There are some regions where forages like perennial ryegrass will work. In terms of cool-season grasses, perennial ryegrass is one of the highest-energy grasses available. These types are utilized in New Zealand and Ireland/Great Britain. They will often have a fiber content 5 to 10 percent lower than typical cool-season perennial grasses,” Brink says.
Growing conditions in New Zealand and Ireland are ideal for these ryegrasses. “They have the moisture, sunlight and cooler temperatures – without the extreme cycles in temperature that we have,” Hall says. In northern climates, we must be selective in the forages we choose, so they won’t die out over winter.
“Here in Wisconsin, perennial ryegrass is often sown when a producer establishes a new pasture, as a means of increasing yield during the first growing season,” says Brink.
“Producers realize that, within a couple years, the amount of ryegrass in that pasture may be significantly less. It often doesn’t have the cold tolerance we need, nor summer drought tolerance,” he says. It is often added to the new seeding, however, because it establishes so rapidly the first year and gives cattle excellent forage while the other plants are growing.
“This brings up the importance of how you manage the grazing,” says Hall. “What you do in terms of fertilization and grazing management may help ensure more chance for getting the feed you want,” she says.
“Beef producers must understand the nutrient needs of growing animals because sometimes they are shortchanged in pasture management,” Brink says.
A pasture grazed at a more vegetative stage (young and growing versus mature) will provide more energy because the fiber level of the plant is lower than in mature grass. A growing beef animal will consume mature grass, but the quality may not be high enough to produce much weight gain.
Hall says it all boils down to how much the animal can consume of the given forage. “If it is too mature, there is a limit to how much they can eat simply because the material will fill up the rumen (and doesn’t break down as quickly during digestion), and the animal can’t eat enough,” she says.
“We have to look at how much they can eat and factor in the composition of the forage to know whether they get the pounds of digestible nutrients and protein they need to support the performance desired,” says Hall. 
Heather Thomas is a freelance writer based in Idaho.
PHOTOS
PHOTO 1: Cattle gain well on high-quality pasture.
PHOTO 2; A mix of a high-energy grass and clover, in a green growing stage, provides excellent forage for finishing beef. Photos courtesy of Dr. Brink.
Plant sugars
Clayton Robins, executive director, Manitoba 4-H Council, has researched forages for a number of years. In 2008, he was part of a team from Canada that went to Argentina to look at forage-fed beef production.
“We spent most of our time with Dr. Anibal Pordomingo, a renowned beef and forage scientist who was our guide and translator. He showed us a slide that demonstrated plant water-soluble carbohydrate (sugar) levels in cereals as they advance physiologically,” says Robins.
“As the sugars changed, animal gain also changed, in a linear relationship. As the sugars went up, animal gains went up, to impressive levels. We had been struggling with how we could make forage-finishing work as part of our research program. That was a lightbulb moment, realizing we needed to look at plants differently,” he says.
“We did some evaluations at the Brandon Research Centre while I was still there. Later I went to many of the regions of the world that practice longer grazing times than we do, with more emphasis on looking at plant sugars and other forms of energy in the plant. We tend to focus more on fiber in North America. I looked at some of the plants other countries were using and the influences those plants have on ruminant digestive efficiency,” Robins says.
His report discusses all aspects of energy-dense forages. “One of the interesting things that has phenomenal potential, if we can make it work, is the ability to initiate early development of marbling cells in young, developing animals."
"A lot of research at this point has been done with early weaned calves fed high-energy diets, but I wonder if we can get that same effect under grazing, with a calf still on the cow – rather than feeding grain or some other high-energy supplementation. It requires a sustained supply of high levels of energy to trigger the phenotypic and physiological responses.”
Trials are under way in New Zealand, using energy-dense forages, to determine that potential. “The studies will be assessing early weaned calves, beef and dairy, eating forage instead of concentrates/grain to achieve these results.
They will evaluate impact on carcass quality and earlier time of slaughter – with the expectation of improved marbling,” he says.
Robins continues to look at various energy-dense species like tetraploid Italian ryegrasses (which are capable of accumulating the greatest amount of plant sugars, of all the grasses) along with chicory and forage plantain, as well as a few legumes.
