by Beth Ellen Doran
ISU Extension and Outreach Beef Program Specialist
Cow-calf producers will have an abundance of corn stalks to graze and harvest this fall. This is good news, considering a year where drought has reduced the yields of grain, hay and pasture.
But, grazing and managing this year’s stalks will not be “run-of the-mill.” Drought, coupled with several wind and hail storms, has taken its toll on stalk strength. Consequently, producers need to be cautious when grazing corn fields as there will likely be more corn remaining in the field. This can lead to over-consumption, digestive problems, and founder (stiffness in the animal). Given too much corn, cows can die.
However, there is an easy way to estimate how much “down” corn is in the field. An 8-inch ear of corn contains about a half-pound of grain. Using that estimate, 112 ears would equal 56 pounds or one bushel. If corn is planted in 30-inch rows, counting the number of ears in three different 100-foot furrow strips and dividing by 2 will give an approximate number of bushels per acre. Count small or broken ears as half ears and very large ears as one and a half.
Any amount of remaining corn beyond 8 – 10 bushels per acre requires a well-planned grazing strategy to limit grain consumption. This may mean stocking more than one animal per acre or fencing off strips in the field to increase animal density.
The other problem with grazing stalks is the potential for nitrate toxicity. During a drought year, nitrates can accumulate in the stalks which when eaten by the animals can cause problems with their oxygen-carrying capacity and ultimately death.
Fortunately, taste preferences of the cow will help control this problem. Cattle prefer to first eat remaining corn grain, followed by husks and then leaves. The stalk is least-preferred. This, too, is good because the grain, husks and leaves are also the more nutritious parts of the corn plant.
However, if you plan to graze corn stalk fields this fall and winter, I still recommend testing the combined stalks for nitrate level. Drying of the corn stalks will not reduce the level of nitrates in the stalks. It may gradually diminish if there is sufficient rain to leach the nitrates over several weeks or months. But, to date there has been little rain to accomplish leaching.
If the lab confirms higher levels of nitrates, there are some best management practices that can be implemented in grazing the stalks. Observe what the cows are eating. When they have eaten the ears, leaves and husks, move the cows to a fresh field. Do NOT force them to eat the stalk. Another best management tip is to provide other “clean” forage or feed while grazing corn stalks.
Good management will also help with cornstalk bedding. Feed the animals their ration first and have the cattle full before placing dry cornstalk bales in a pen. This will help prevent animals from over-consuming stalks and reduce the potential for nitrate toxicity.
Grazing cornstalk fields may be more challenging this year, but they are still a low-cost source of cow feed that can be successfully utilized when managed well.