Brad Schick, Nebraska Extension Educator

• There are 8 lbs 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.

Having corn stalks 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 can also 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 corn stalks 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% TDN (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 is 16 lbs 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 will also be lost to trampling, defecation, and other considerations such as wind. Now the calculation is 8 lbs 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 bu/ac corn. By the calculations, there is 1600 lbs of dry matter per acre available (8 lbs X 200 bu = 1600 lbs). A 1000 lb animal will consume about 26 lbs of dried forage per day which means a 1300 lb animal will consume about 34 lbs 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 lbs for the 1300 lb animal. So, how many days of grazing is that? By the calculations, there are 61 days of grazing for one cow grazing one acre (1600 lbs DM ÷ 26 lbs = 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 can be also be a great option but 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 is also 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 will likely 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. A way to allocate grazing with excessive corn is seen below.

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.

Interviews with the authors of BeefWatch newsletter articles become available throughout the month of publication and are accessible at https://go.unl.edu/podcast.

University of Nebraska-Lincoln