As corn harvest wraps up and fields open for grazing, there are several things worth checking before animal turnout. Corn residue can be a valuable, low-cost feed resource, but conditions this fall could affect both the amount and quality available.
First, fungal diseases have made noticeable impacts on corn fields in Nebraska this year. Fungal leaf diseases like tar spot and southern rust can cause early leaf death, while stalk rots weaken plants and increase the potential for lodging. With some fungal diseases, residue quality may be somewhat lower. However, the bigger concern is that there may simply be less leaf material left. Along with husks, leaves are the primary component of residue-based diets. Their loss can shorten the window of quality grazing.
Another concern is downed corn. Stalk rots, wind damage, and harvest losses may leave more grain in the field than normal. Cattle will seek out that corn first, and too much at once can lead to acidosis, or grain overload.
So how much corn is too much? Nebraska Extension has a simple way to estimate it. In fields planted in 30-inch rows, count dropped ears along three separate 100-foot row sections. Add those ears together and divide by two. For example, 30 ears would mean about 15 bushels per acre left on the ground. Check several locations since losses can vary.
Once you're above eight to ten bushels per acre, precautions are needed. Gradually adapting cattle to grain before turnout and strip grazing to limit access are two ways to reduce risk. If you want more detailed information on managing downed corn, UNL’s Dr. Mary Drewnoski has a great article titled “Dealing with Down Corn” at the beef.unl.edu website.
If you're already out counting ears, keep an eye out for moldy ears. While visible mold doesn't necessarily mean mycotoxins are present, and clean-looking grain isn't a guarantee they're absent, large amounts of moldy grain and ears warrant a closer look. Lab testing, while expensive, is the only reliable way to determine mycotoxin levels.
Nitrates are another concern, particularly in drought-stressed corn. Nitrates tend to accumulate in the lower stalk, while the grain, husks, and leaves cattle prefer are generally much lower in concentration. Avoid turning hungry cattle onto suspect fields or leaving them long enough that they're forced to eat stalks. If drought stress was severe, especially in stunted areas, consider testing questionable material before grazing.
Finally, remember that residue quality declines as cattle graze. Once the grain, husks, and leaves are gone, what's left is lower in energy and protein. Dry cows in good condition may do well early in the grazing period, while lactating cows and younger animals may need additional supplementation. Monitor body condition, residue availability, and adjust grazing duration accordingly.
Evaluating disease damage, downed corn, and nutritional needs ahead of turnout can help make the most of crop residue while maintaining livestock performance.
Ben Beckman is a beef systems Extension Educator serving northeast Nebraska. He is based out of the Cedar County Extension office in Hartington. You can reach him by phone: (402) 254-6821 or email: ben.beckman@unl.edu.
