Having cornstalks to graze is a great resource for livestock producers. For dry cows, it is a relatively inexpensive feed that can typically meet, or come very close to meeting, nutritional needs. Grazing also can help get rid of corn remaining in the field and potentially reduce volunteer corn the following year. But are cattle really grazing stalks?
Yes and no. In everyday conversation, grazing cornstalks is said, but the stalk is the last thing cattle eat. Cattle do eat stalks, particularly if they are left on a field too long, but they are primarily consuming leaf, husk and leftover corn.
The stem or stalk makes up about 48.5% of the residue, while the leaf blade and husk make up 39.6%. Cattle will consume leaf and husk if available. That diet will consist of 52% to 55% total digestible nutrients and 5% to 5.5% crude protein.
When thinking about how long to graze corn residue, the calculation to follow is that for every bushel of corn produced, there are 16 pounds of dry leaf and husk. The recommended grazing plan should be to remove 50% of the leaf and husk.
This assumes that portions of the forage also will be lost to trampling, defecation and other considerations such as wind. Now the calculation is 8 pounds of good forage on a dry matter basis that is available for consumption for every bushel of corn.
For example, say the field produced 200 bushels per acre of corn. By the calculations, there are 1,600 pounds of dry matter per acre available (8 pounds × 200 bushels = 1,600 pounds). A 1,000-pound animal will consume about 26 pounds of dried forage per day, which means a 1,300-pound animal will consume about 34 pounds per day.
However, with lower-quality forage such as corn residue, intake will be closer to 2% of bodyweight. In this example, that means closer to 26 pounds for the 1,300-pound animal. So, how many days of grazing is that?
By the calculations, there are 61 days of grazing for one cow grazing 1 acre (1,600 pounds dry matter ÷ 26 pounds = 61 days). A general rule is about 30 cow days per 100 bushels of corn produced. Grazing corn residue can be a very cheap way to potentially clean up corn in a field as well.
Calves and replacement heifers also can be a great option, but they will need a protein source in order to meet their growing requirements. Not only is grazing corn residue good for the cattle producer, but it also is good for the crop producer. Studies from the University of Nebraska-Lincoln have shown that grazing corn residue increases or at least maintains crop yields. (Grazing Corn Residue: A Win-Win for Crop and Cattle Producers).
In years when there is ear drop, plants blown over or other factors, the calculations likely will need to be adjusted. That is when good observation is critical. Checking how much corn is on the ground can help with supplementation costs, if needed, and to make sure cattle are safe to graze corn residue.
A way to calculate the amount of corn on the ground is found in the article Estimating Bushels of Corn on the Ground by Counting Ears Prior to Grazing with Cattle. Grazing corn residue, done right, can be very beneficial to the cow and the producer’s bottom line. An accurate calculation will reveal the amount of forage available and will aid in management decisions to be followed.
Factor to consider:
- There are 8 pounds of grazable dry matter per bushel of corn.
- Leaf and husk make up 39.6% of the dry matter in corn residue.
- Intake on corn residue fields will be close to 2% of bodyweight.
- Check questionable fields for excessive corn before grazing.
Schick is a Nebraska Extension educator.