There's good news and bad news about corn silage hybrids, says Mike Hutjens, University of Illinois extension dairy specialist.
“The good news is that when dairymen ask, ‘Should we be looking at corn silage varieties?’ today the answer is yes, they should. That answer has changed over the years because the seed companies have done a yeoman's job of really looking at alternatives and stacking traits.”
The bad news, Hutjens adds, is that silage composition varies more than ever before, and dairy producers and nutritionists must account for those differences when formulating rations.
“Corn silage is not corn silage is not corn silage,” he states.
“There's been a kind of paradigm shift because we had always heard that we needed high energy with a lot of grain in the ration to get milk production,” says Marcia Endres, a University of Minnesota dairy scientist.
But some of today's silage hybrids are highly digestible, she says.
“We now are seeing that more forage and less grain can still achieve high production,” she comments. “Plus, the cows can be healthier because the rumen gets more fiber.”
Hutjens challenges dairy producers to declare before planting which cornfields will produce silage. This should be planned carefully based on variety selection.
“It should not be decided in August or September, because a certain field won't make grain due to drought damage or weed pressure, lateness of harvest or other factors that make it the poorest crop. That's not a valid reason to choose it for silage.”
Hutjens says producers making decisions about silage hybrids should look seriously at what he calls “the big four”:
Yield. You can't afford to give up much yield or you lose too much in nutrient and dollar value for that acreage.
Digestibility. Look closely at digestible fiber. How digestible is that corn plant itself — the stalks, leaves, etc. In many silage hybrids, that accounts for 50-60% of the dry matter.
Starch. Starch is essential for what it does in the rumen in terms of dry matter intake, fermentation profile, microbial yield and the types of volatile fatty acids being produced.
Hutjens points out that physiological tradeoffs occur in the corn plant. To produce starch, the plant must utilize energy from plant tissue. Conversely, energy retained in plant tissue could reduce starch development. A good silage hybrid strikes a balance, but there can be wide variations.
Agronomic factors. Consider hybrid traits and features, such as resistance to blight and other diseases. Input traits such as resistance to insects (Bt) and herbicides (LibertyLink and Roundup Ready) also directly influence the economic success of your silage crop.
Endres points out that hybrid genetics are only a part of the silage equation.
“It's important to keep in mind that, besides which hybrid was planted for silage, the harvest and storage methods, feeding management and ration formulation, agronomic practices and growing conditions will each have a major impact on the nutritional quality of the resulting silage.”
Some hybrids are commercialized primarily for silage production, such as brown midrib (BMR) and leafy, she continues, and more silage yield and quality evaluation has been done on conventional hybrids in order to help producers select which ones might work best for silage.
Gerrit DeBruin, dairy nutrition consultant for Prescription Premix, Lake Mills, WI, has had vast experience with BMR corn silage in dairy rations.
“Those are by far the best and healthiest diets I have put together,” says DeBruin. “The main advantage is that BMR enables addition of higher caloric density through forage. And whenever forage content in the diet increases, usually good things happen from a metabolic standpoint.
“My highest-producing herds have BMR as a common denominator,” he reports.
Selecting BMR hybrids is a bit like choosing dairy bulls with strong feet and lets, says Hutjens.
“We don't get milk from feet and legs but we know they're important,” he says. “Brown midrib corn is similar. It does have yield drag and the producer has to weigh how much the higher quality of BMR translates into milk.”
He figures herd production is a big factor in BMR economics. The best payback from those hybrids probably is in high-producing herds.
Rations should be balanced differently when using special silage hybrids, Endres points out. BMR brings higher fiber digestibility, and some leafy hybrids are more digestible than others. So the silage should be properly analyzed.
“When we harvest corn silage, we need to go back and evaluate some of those characteristics for which we selected the hybrids we planted,” says Hutjens. “That brings us to three fairly new tests that provide more insight into feed value and palpability and the shelf life of corn silage.
“In vitro tests determine digestibility of the fiber, so instead of just using an estimated energy value off a fiber component like ADF or NDF, we can actually consider what's going to happen in the rumen,” he continues. “Some of those tests — 24-hour in vitro, 30-hour in vitro, 48-hour in vitro — have grown very popular in the last couple years. There are some great discussions under way among the academics about these, but the point is we are trying to find, before we feed it to the cows, what kind of digestibility or energy value we can expect with that corn silage.”
That's vital this year because a lot of corn was planted late, or was stressed by drought or flooding. There probably are huge differences in silage quality and composition.
Starch should be analyzed because it can vary widely based on growing conditions and has a dramatic effect on ration formulation. NDF digestibility also is important for estimating energy content, says Hutjens. And pay attention to more standard tests, such as NDF, ADF, protein, mineral fractions, etc.
Fermentation analysis can be an important tool, too, according to Hutjens.
“I look at the volatile fatty acid profile — lactic acid, acetic acid, ammonia levels and pH — to gain insights about palatability, how well this crop has fermented and how much stability I can expect in that crop at feed-out time.”
He's excited about Milk 2000, a tool developed at the University of Wisconsin.
“Instead of looking at these massive numbers and data sets, it allows farmers or the extension service to run test results through an equation to estimate how much milk per acre and how much milk per ton of silage you can anticipate.
“Success with corn silage all boils down to three windows of opportunity,” he concludes. “Seed selection, luck with the growing season, and being able to ensile and preserve the crop properly. If the producer can manipulate, manage and luck out on all three, then there are no big surprises in October and November when he opens up the silo and can say, ‘Man, we have a winner.’”