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Greenchopped corn to cover forage shortages

Eric Mousel Published on 04 March 2014

Many areas of the country have been dry again this past summer, leaving livestock producers with short pastures and declining grass quality. For many operators, hay inventories are critically low.

Although the southern U.S. did see some improvement in the near decade-long drought, roughages of all types remain in scarce supply. As a result, many livestock producers are finding that buying additional roughage is really not practical from a supply or cost perspective.

This past year also saw many areas in the country where most everyone had at least some corn that was planted really late due to the cool, wet spring, and the threat of it not reaching maturity became very real as fall approached.

This situation led many operators to chop a portion or all of the late-planted corn to stretch out roughage supplies for a few months until stalks could be baled or other alternatives became available.

Greenchop versus silage
As many operators have discovered, it is important to differentiate between greenchopped corn and corn silage, because they are not the same thing.

Greenchopping is harvesting fresh, green forage right out of the field at whatever moisture content the forage is at the time. In most situations where corn is greenchopped, moisture content will be 80 percent or more, leaving less than 20 percent dry matter.

Conversely, silage is chopped at around 65 percent moisture to encourage the ensiling process for long-term preservation and storage of forage quality.

The bottom line is that when the moisture content of chopped forage is in excess of 80 percent, the forage will not effectively ensile. Therefore, storing large quantities of greenchopped corn right out of the field will result in a lot of seepage, and ultimately spoilage, and the majority of your efforts will be wasted.

Although it should be noted, research from the University of Minnesota has demonstrated that greenchopped corn can be effectively stored in properly sealed silage bags, the cost of doing so likely is not very competitive.

So, can corn be greenchopped right out of the field and fed to livestock? Yes it can, but you won’t be able to store it in a pile for long periods of time like corn silage.

My recommendation is to cut about two to three days’ worth of greenchop and feed that up before chopping more. Although not the best scenario in terms of labor and resource use, it likely is the best option available to limit the amount of greenchopped corn lost to spoilage.

If you rely on a custom chopper, greenchopping corn is probably not going to be a practical solution for you.

Another scenario to be aware of involves nitrates. Most corn that was greenchopped this year was chopped because of late planting and high soil moisture conditions lasting well into summer, so nitrates were not really a concern.

However, a more common situation is greenchopping corn because soil conditions are dry and either a complete loss of the crop is a possibility or roughage for livestock is not available.

Corn is a fairly effective nitrate accumulator, and this condition is intensified by dry soil conditions. Forage chopped with high nitrate concentrations (more than 2 percent nitrate-nitrogen) can lead to nitrate poisoning when fed to livestock.

Like most nitrate-accumulating plants, the highest concentrations of nitrate will be found in the lower one-third of the stalk. Therefore, corn-plant nitrate levels should be tested prior to greenchopping to determine the threat level for livestock.

Furthermore, raising the cutter bar on the chopper to 8 to 12 inches will substantially reduce nitrate concentration in the forage. Greenchopped corn that contains higher nitrate concentrations can be mixed with other roughages to reduce nitrate levels in the diet.

If nitrate levels are really high (more than 3 percent), talk to a ruminant nutritionist before feeding to make sure diets are effectively blended to reduce the threat of nitrate poisoning.

Although the best use of corn for forage is silage because of its storage potential, greenchopped corn can be effectively managed to bridge the gap in your forage program.  FG

Eric Mousel
Eric Mousel

Extension Cow-Calf Educator University of Minnesota
North Central Research and Outreach Center