Grazing Hail Damaged Cornstalks

As found at http://beef.unl.edu


Beef Cattle Production

Frequently Asked Questions

Q: A lot of corn on the ground in a hailed field. How much area at a time should you feed to thin cows to clean up the field? Is there a bloat supplement to curb eating?


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A: Anytime more than about eight bushels of grain per acre are left in the field after harvest, cattle grazing the stalks risk getting acidosis and founder. Both diseases are caused by excessive grain intake, which increases rumen acid production. This can cause severe foot and hoof problems, including lameness. While smut is not a health problem, some grain may contain other molds that can produce mycotoxins. Vomitoxin and fumonisin rarely cause problems for beef cattle at typical contamination levels and aflatoxin rarely occurs in risky concentrations in Nebraska grain crops. Still, if there are reasons to suspect much mycotoxin may be present, an assay of the grain would provide useful safety information. Estimate the amount of corn down in a field. An 8-inch ear of corn contains about one-half pound of corn grain so it takes 112, 8-inch ears to equal 1 bushel (1 bushel = 56 pounds). Thus, by counting the number of ears, the amount of corn can be estimated. For corn planted in 30 inch rows, count the number of ears in three different 100 foot furrow strips and divide by two to give an approximate number of bushels per acre. Small ears and broken ears should be counted as half ears, while very large ears could be counted as an ear and a half. Any amount beyond 8 bushels per acre will require a well-planned grazing strategy.

One strategy for using high-grain cornstalk fields is to minimize availability of grain to susceptible animals. A good way to do this is to first graze yearling cattle, calves, or cull cows destined for slaughter, then follow with cows. Another alternative is to graze only a few hours per day. You also could strip graze the field to force cows to consume some husks and leaves along with the ears of corn. A final strategy might be to feed some grain or ear-corn seven to ten days before cattle are turned out to help them adapt to a high-grain field.

One factor influencing the success of these stalk grazing strategies is the experience level of the cattle grazing the field. Old cows with previous experience in cornstalk fields can pick up amazingly high amounts of corn in a short period of time, as can experienced yearling cattle. If they have not been conditioned to eating a high grain diet, some of the previously listed strategies may fail. Thus, inexperienced calves may have the least risk of founder or acidosis in high-grain cornstalk fields because they must first learn how to find corn. As a result, their grain intake safely increases gradually.

Bloat is usually not a concern with cows grazing residue with excess corn.

In hailed damaged corn fields, nitrates could be a concern. The nitrates are usually confined to the stalk and in-particular the lower 6 to 8 inches of the stalk. In a stalk field grazing situation, cattle commonly select the stalk last to eat, after the corn, husk and leaves are eaten. Our experience is that as long as cattle can select corn, husks, and leaves, more than 50% of their diet will be these three items. My recommendation would be to fill pregnant cows up with forage (hay) before turning the into this stalk field and do not graze it so long or hard that you force cows to eat the stalks.

October 16th, 2009
Dr. Rick Rasby, Professor of Animal Science
Animal Science, University of Nebraska - Lincoln, Lincoln, NE