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Nitrates a concern when chopping drought-stressed corn for cattle feed PDF Print E-mail

By Robert Tigner
SW4 Agricultural
Extension Educator

Forages for southwest Nebraska beef herds will be in short supply this year and with some dryland corn that has become severely damaged due to drought, there are some considering using that dryland corn as feed for cows.
There are some cautionary notes that producers need to heed if they do so.
When chopping corn for silage, cut at a stubble height of 12 inches to leave the corn stalk with the highest nitrate concentration. Ensiling corn can reduce nitrate concentration by up to 50 percent.
Chop and ensile corn at 35-40 percent moisture just as you would normal corn silage. Drought-stressed corn often has a higher moisture content than anticipated. Do some moisture tests before chopping.
An inoculant will help the fermentation process and is more important to use on drought stressed corn.  
If you decide to chop corn for silage, don’t do it right after a rain. Rain will transport more nitrates into the surviving corn; wait a few days after rainfall to begin chopping.
What about feed value? It is better than you might think.
The attached table of information gives some indications as to the value of drought-stressed corn. This is important to consider for buyers and sellers of drought-stressed corn.
Buyers should not pay more for corn than its value compared to other feeds you may be able to purchase. Several University extension spreadsheets are available to make the necessary calculation.
Call me at the Chase County Extension office, Imperial, NE, 308-882-4731 for help with the spreadsheets.
If you decide to graze or greenchop corn for feed, introduce the forage slowly by limit feeding. Feed dry hay to cattle just before letting them graze corn and thus dilute the nitrates in the corn.
You can gradually lower the hay offered first while the cattle get used to the nitrate content. Greenchop daily so that the nitrate is not converted to nitrate which is more dangerous to cattle.
If grazing corn, don’t allow cattle to eat the lower 10-12 inches of stalk. That part of the corn stalk has the most nitrates. Remove the cattle as soon as they consume all the leaves.  
Also limit the amount of corn cows can access by electric fence. Moving the fence daily is preferred. This will help limit the nitrate consumed by cows.
Grazing drought-stressed dryland corn is not recommended, however. Don’t overgraze dryland cornstalks this winter; nitrate content may still be too high.
Hay may be the most difficult method of mechanical harvest, especially when ears have started to form—the stalk and ears will be slow and difficult to dry.
Use a crimper when windrowing to increase the drying rate. Unlike silage, nitrate levels do not decrease in hay after it is baled.
Some of the nitrate risk can be reduced by leaving eight inches of stubble. Tall stubble will elevate the windrow aiding in drying.


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