Feeding corn silage to cattle comes with some risks in Alberta — but there are ways you can manage that.
“There are a lot of different factors that will affect yield and quality in corn silage,” said federal research scientist Karen Beauchemin.
“You have some control over some of these factors, but not all. So to minimize risk, it’s important to understand these factors and focus on the ones that you do have some control over.”
And while things such as agronomics, best management practices, and the growing environment all have a role to play in producing high-quality corn silage, the most important factor is choosing the right corn hybrid for your location.
“You need to select a hybrid adapted to the corn heat unit rating of your location,” added Vern Baron, also a research scientist with Agriculture and Agri-Food Canada. “That’s probably the most important decision you need to make.”
Corn is a relatively new crop to Alberta, which has lower corn heat units on average than other corn-growing regions. While new shorter-season varieties are starting to hit the market, it can still be a challenge to get corn to maturity in most of the province.
And that can make all the difference when you’re feeding cattle.
“In shorter growing areas, there is a trade-off between yield and quality,” said Beauchemin, who presented alongside Baron in a Beef Cattle Research Council webinar last month.
“If you’re a feedlot producer and corn is included in the diet of finishing cattle as a roughage source or a source of effective fibre, quality probably doesn’t matter too much. But if you’re feeding corn silage to cattle as a main energy source, quality becomes very important.”
Because corn silage is more expensive to produce than barley silage — almost twice as much — maximizing the energy content per tonne of feed is vital, said Baron.
“Corn is higher quality, but you have to make up for a difference in the expense of growing it with the yield and concentration of nutrients derived from your investment,” he said.
That means shooting for high starch content (which comes from the cobs) and high digestibility of the fibre (which comes from the leaves, husk, and stalk).
“The nutritional value of corn silage will really depend on the proportions of starch and fibre you get — how much cob versus fibre — and how digestible each of those components is,” she said.
“There’s a lot of variability in the nutrient composition of corn silage, and that variability will increase if you’re growing corn silage in a shorter growing season area.”
Early in the growing season, the plant is only leaves and stalk, but as the season progresses, the cobs begin to form and fill with grain. The more grain there is, the more starch you have in your silage.
“If you have a hybrid that requires a long growing season to mature or if you harvest it early, then the starch content is going to be low, maybe 20 per cent,” Beauchemin said.
“If you have a hybrid that matures fast or if you have a longer growing season, the plants are going to be at a later stage of development at harvest, and you’re going to have more starch, maybe 30 per cent.”
In the western Prairies, that starch level is on average about 24 per cent. That varies based on the growing conditions, the hybrid grown, and the location.
“Our corn silage tends to have less starch and more fibre. As a result, the digestibility is considerably lower in a shorter-season area,” said Beauchemin, adding corn silage with a starch content below 10 per cent would be similar to feeding a low-quality alfalfa or grass hay.
“If you’re getting a value for starch content below 10 per cent, you’re probably growing the wrong hybrid, or you should perhaps think about growing a different forage.”
And feeding that lower-quality corn silage will directly impact animal performance — and your bottom line, she added.
“With a 32 per cent starch silage, you could expect almost 1.5 kilograms of gain per day, whereas with the 20 per cent starch silage, you would be at about one kilogram per day of gain,” she said.
“To get the same gain with that 20 per cent starch silage, you’d have to feed a ration that was about 50 per cent corn silage and 50 per cent grain.”
So how can producers maximize starch content in regions with a shorter growing season?
By harvesting at the right time.
“The goal when you harvest the material is to have cobs that are going to be at the right stage of development to maximize your starch content,” said Beauchemin. “To do that, you want to be at a half milk line or more.”
But more importantly, corn silage should be harvested at the right time to get the optimum dry matter content for ensiling — about 32 to 38 per cent dry matter.
“Regardless of the starch content of your silage, the optimum time of harvest has to be to ensure optimum fermentation, and that has to be driven by the dry matter content at harvest,” she said.
Then it comes down to proper silage management. That means maintaining low pH levels, high lactic acid concentrations, and an oxygen-free environment to preserve the silage. To achieve those conditions, producers should finely chop their material, pack it well in the silo, and then cover it quickly.
“Regardless of the hybrid you grow, the agronomics that you use, and what the nutrient composition is, you have to use good silage management,” said Beauchemin.
“If the cattle won’t eat the silage because it’s poorly fermented, then the energy content of the silage really doesn’t matter at all.”