Cows on corn need attention

Standing corn can be beneficial, but producers must monitor what the animals are eating

MEDICINE HAT, Alta. — The cobs in a field of grazing corn are like ice cream for cattle.

Left to their own devices, cows and beef calves new to a field of standing corn will go straight to the cobs, eat them first and then consume the rest of the plant later.

That’s why Bart Lardner, senior research scientist at the Western Beef Development Centre in Lanigan, Sask., recommends limited access for cattle in grazing corn, at least in the early stages.

Lardner told the Farming Smarter conference in early December that WBDC research has provided insights into the practice, which is gaining popularity on the Prairies now that corn breeding allows plant maturity with lower heat units.

“Some of the advantages of corn … is because it really is producing two and half, three, three and a half times the biomass that small grain cereals do per acre, and so that’s the attraction in terms of dry matter,” said Lardner.

“So there’s a potential there to reduce your cost per cow per day.”

Corn can provide adequate energy and protein for gestating cows in fall and winter, although supplements may be required depending on the stage of pregnancy.

“One thing we have noted with the nutritive value of whole plant corn is that it can be a little bit low on protein. Certainly work with a nutritionist to look at the protein requirements of that cow in the third trimester of pregnancy and even getting very close to calving,” he said.

“The corn crop may not be meeting those protein requirements of that cow in late gestation.”

The ice cream effect is also a risk because loading up on corncobs with high starch content can lead to rumen acidosis and possibly death.

Lardner said producers should use portable fencing to limit cattle access. Cows need to consume 30 to 40 pounds of feed per day, so producers can calculate a three or four day feed allocation based on herd size.

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Gordon Frank, a farmer and Pioneer representative in Brooks, Alta., said the acidosis risk might become less of a worry in herds accustomed to corn grazing.

“Once they figure out that you’re not going to take them away from it, and they know there’s going to be cobs there tomorrow and there’s going to be cobs the next day, they don’t get quite so greedy to go after just cobs,” he said.

“It’s just the first week or two, and then they kind of settle in more.”

Frank said feeding cattle well before turning them into a new cornfield can help, as can supplemental hay in the same field.

Lardner made a similar recommendation.

“What we tend to do at Western Beef is that with cows that have grazed corn, or even naïve cows, we’ll put them out there and we’ll supplement with a fibre source, some round bales.”

Frank said corn grazing has increased in southern Alberta, primarily because of the availability of new hybrids.

There are jokes about “holiday corn,” meaning cattle producers with standing corn crops can take a winter vacation while the cattle feed themselves.

“It does reduce the maintenance,” said Frank.

“You’re not starting tractors. You’re not hauling out bales, you’re not doing a lot of that stuff … plus you’re getting more yield per acre than any other crop we can grow.”

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The tricky part is choosing a variety that will provide the best feed value at freeze up. Because that date varies, some producers plant an early variety and a later variety.

“You can juggle it a bit. You’re sort of hedging your bets,” he said.

“It works good for quite a few of our guys (customers).”

Lardner suggested planting a variety that requires 100 to 200 heat units more than the area’s average. That way, the corn might have the right level of maturity for best feed value when the first killing frost comes.

“That plant is hopefully in that early milk line or half milk line state,” he said.

“We feel that the half milk line, or the R5 stage, is somewhere equivalent in terms of the amount of starch per acre and the amount of fibre per acre.”

Corn that is too mature at freeze-up doesn’t offer as much to grazing cattle. It may have more energy content, but more grain will likely pass through the cattle without being fully digested and used.

Frank urged growers to get their variety choice and agronomy right. Corn is more expensive to grow than other cereals and forage. The seed alone can be about $100 per acre, and there are other inputs after that.

It means it has to pay off if grazing is the plan.

“It is a little more costly to grow than barley or alfalfa, but what else stands there through thick and thin and is grazable,” he said.

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Contact barb.glen@producer.coma