If a cow is grazing, you don’t have to feed it.
It’s a deceptively simple statement, and the basis for many cattle producers looking at extended grazing to cut costs. Farmers have looked at bale grazing, forage stockpiling and swath grazing, among others; but another grazing system has caught the interest of some beef producers, standing corn.
More commonly a cash crop in Manitoba, researchers and farmers have honed in on corn for grazing, hoping to capitalize on its high yield and energy content.
Bart Lardner, senior research scientist with the Western Beef Development Centre in Lanigan, Sask., is among those who would like to see more cows in the cornstalks during winter.
“Why would you graze standing corn? Well, you’re doing two things,” he said during an Oct. 12 webinar on the subject, put on by the Beef Cattle Research Council. “You’re trying to reduce the cow cost per day. We’re also trying to capture those manure nutrients.”
In a test of five corn varieties in 2011-12, Lardner found standing corn yielded an average five tonnes of dry matter per acre, about double the dry matter from cereals, and grazing costs ran between 70 cents and $1.42 per head per day.
The Western Beef Development Centre estimates corn grazing is 26 per cent cheaper than moving cattle back into the lot and beats out bale grazing barley (a practice it estimates is eight per cent cheaper than drylot overwintering). Swath grazing barley, however, drew almost even with corn at 25 per cent cheaper than drylot.
In an industry where feed cost is among the greatest expenses, those numbers appeal.
Energy, likewise, highlighted corn.
According to 2015 data out of the University of Saskatchewan, total digestible nutrients in corn averaged 64.6 per cent over three years, compared to 60.6 per cent in swath grazed barley and 57.2 per cent in barley greenfeed.
Protein, however, fell short. Corn had the lowest protein of all three feeds at 8.2 per cent, compared to 11.2 per cent in grazed barley and 10.9 per cent in drylot feed.
Lardner’s corn variety trial echoed that trend. His plants averaged 7.4 per cent protein and 69.4 per cent total digestible nutrients.
“Protein is a little bit low on the corn, especially for a gestating beef cow coming into calving,” Lardner said.
Intercropping legumes may be an answer to that problem, he later told his online students. Otherwise, some protein supplements may be needed.
Good for the soil
Overwintering systems in general have been a good news story for soil nutrition.
In a comparison of bale grazing, bale processing and applied manure, the Western Beef Development Centre found that overwintering cattle had a larger increase of nitrogen in the first six inches of soil than either a 30-ton-per-acre manure application or 10 tons per acre of compost. The next year, cattle overwinter sites increased forage dry matter yield by 270 per cent which compared to a 60 per cent increase on sites where nutrients were applied.
Lardner’s research suggests that grazing corn can, likewise, help recover nutrient-deficient land.
Growing corn is not without challenges, particularly in a province where not all farmers are familiar with the crop and the risk of early frost may make some beef producers balk.
It is a high-input crop, Larder warned, urging producers to seek out agronomists and seed reps to choose the right variety and management.
Lardner referred to the “milkline,” the point where a corn plant moves starch into the kernels out from the cob’s core. The resulting colour change is easily seen when a cob is cut in half.
In grazed corn, that milkline should be halfway through the cob at freezing for the best nutrition, Lardner said. Variety should be chosen with that in mind.
“I strongly, strongly suggest if you’ve never grown corn, start small — five to 10 acres in year one,” Lardner said. “Get comfortable with this. You have to get used to growing corn. You have to be comfortable with it. The cows have to be comfortable with grazing it.”
Manitoba’s brutal winter adds in another wrinkle. Stalks alone will not provide enough wind relief in a climate where wind chills commonly dip below -30 C and windbreaks and a close water source will be a critical part of making the system work, Lardner said.
Adjusting cattle to corn
For cattle, a cornfield is often unexplored territory.
“Our cows certainly weren’t used to grazing corn when we first put them out there,” Lardner said. “In fact, what they did is they grazed all the dead grass around the fence post and they avoided those cornstalks like you wouldn’t believe. About 24 hours later, one cow went over and took a bite and guess what? It tasted pretty good.”
Farmers may want to add round bales to help transition. Animals should be fenced in with the familiar feed and several rows of corn. The herd can then be weaned off hay.
Once cattle get a taste for corn, there is a different problem.
Cows will be drawn to the energy-rich cobs first, and most cobs in a paddock will be consumed after the first day, Lardner said. After that, cattle will aim for the husks and leaves and will not stoop to eating the stalk until last.
Rotational grazing will keep cattle from gorging on cobs, Lardner advised. After three days, cows should have stripped 90 per cent of edible material in a paddock and be ready to move.
“These guys are very selective about what structure on the plant they’re going to consume,” he said. “They will go after cobs first. They will figure out that’s the ice cream part of the plant. If you give them 40 acres, if you give them 100 acres, they’re going to go out and eat cobs for two to three days. Then you’re going to wind up with issues.”
Too much cob can lower stomach pH, in some cases below the 5.5 baseline for rumen acidosis, according to Lardner’s work.
The potentially fatal illness can cause animals to lose condition, go off feed and experience diarrhea, higher breathing and heart rates, depression and lethargy.
That risk puts a higher priority on transition. Animals should be adapted for a week to 10 days before being exposed to corn and cattle should be fed before going out to the field. Fibre supplements or limiting grazing at first may also lower the risk.
Brian Lemon, Manitoba Beef Producers general manager, said corn grazing is, “not very common, but growing,” in the province.
“It’s certainly something that offers an opportunity for our producers to not bring their animals back in but to graze them for a longer period of time,” he said. “Grazing standing corn, obviously there’s a number of benefits, both in terms of economics — if you can graze your cattle, you’re not feeding them — but also environmentally. The grazing of the animals is just a more sustainable method of raising cattle. When you graze, you put the nutrients right back where they came out of and return them to the soil in a lot more of a closed loop. It’s something that we’re watching.”