Frequently Asked Questions about Grazing Corn Residue Fields with Excessive Downed Corn

Mary Drewnoski, Nebraska Extension Beef Systems Specialist

Prior to grazing cornstalks with cattle, an estimate should be made of the amount of corn that is present in the field. Photo credit Troy Walz.

Putting cows out on corn fields with a lot of corn is a recipe for acidosis (grain overload), abortion, and possibly death, if their rumen bacteria are not properly prepared. Cattle that become acidotic for even a short time can have reduced performance long term due to damage to the rumen wall. Therefore, taking the time to avoid acidosis is very important.

How do I know how much corn is in the field?

If corn is planted in 30-inch rows, count the total number of ears in three different 100-foot furrow strips and divide by two to give an approximate number of bushels per acre. Be sure to do this at multiple locations in the field as the amount of dropped ears may vary across the field.  If the amount of dropped ears is above 8-10 bushels per acre, then proper precautions need to be taken.

If I have a lot of downed corn, what are my options?

In terms of preparing the cattle for eating the corn, the strategy with the least risk of negative effects is to adapt them to corn before turning them out into the field and then strip grazing limited areas.  Feeding cows 2 to 3 pounds of corn and slowly increasing to 10 to 15 pounds over a 10 day to 2-week period will help get them adapted to corn and reduce the risk of acidosis. If you are going to need to move to a new field over the winter (based on stocking rate and the amount of residue in the field), either move them once the corn is mostly used so that they are still adapted when going to a new field with more corn, or split them up such that they graze one field all winter. If cattle run out of corn, they will no longer be adapted and thus, would need to be slowly fed increasing levels of corn, again, over a 10 day to 2-week period before moving to a new field.

Can’t I just add some sodium bicarbonate to the mineral or water?

Sodium bicarbonate and other buffers are NOT an effective acidosis prevention strategy. Using the strategy of feeding corn before turnout as described above is much better use of money and labor.

Can I use a drench (rumen inoculant) to avoid acidosis?

There is a rumen inoculant available that contains the key bacteria which is normally present in grain adapted cattle and to help maintain a higher pH (keep them from getting acidotic).  While there are no data with cows grazing corn, using this product could reduce the risk of acidosis. If strip grazing limited areas in the field is not possible, using the corn feeding adaption described above and then using this product at turn out may be beneficial.