This year in Colorado, it is estimated that 960,000 acres of corn were harvested. Researchers have found that for every bushel of shelled corn harvested there are 50 pounds of residue left in the field. An acre yielding 180 bushels of corn would have 9,000 pounds of residue. Statewide cattle inventory is down, but Colorado still has approximately 2.5 million head, providing many opportunities to graze the residue. If the residue is grazed correctly, it eliminates the costs associated with harvesting and feeding other forages, and can be beneficial for both ranchers and farmers.
Grazing animals tend to congregate around water and mineral sources. To avoid sacrifice areas of compacted soil, move water and mineral sources if possible. Waiting until the soil is frozen to begin grazing will reduce soil compaction as well. However, the nutrient content of the residue decreases with time after harvest and it is recommended to graze as soon as possible. The normal freeze and thaw cycles in the spring can also reduce soil compaction after animals are removed.
Corn grain is often left in the field during harvest. It may be knocked off the stalk by wind or spilled as a truck makes or turn. Volunteer corn growth may rob yields from the next rotated crop. Cattle will preferentially search for corn grain first, reducing next year’s “weed” problem and weed control. Make sure to assess how much corn is in the field prior to grazing. If unusually high amounts of corn have been left in the field, the high starch grain can cause acute acidosis in cattle. If this is the case, it is best to either restrict cattle from the whole field by rotational grazing or adapt cattle to the high corn diet by feeding corn before grazing the residue.
There are benefits to leaving the organic mass of a previous crop residue in the field. As the plant litter decays, it will add nutrients to the soil. However, it is common to see corn stalks and stubble from several years earlier. Grazing cattle in your field will speed up the process turning the plant material into a usable fertilizer, manure, which will be spread throughout the field.
It is important to note that corn stalks are not a high quality feed. Although there is corn grain left over in field, corn stalk residue contains about 65% Total Digestible Nutrients (TDN) and 7.5% Crude Protein. It will continue to decrease in quality from weathering and as grazing animals eat the more palatable parts of the plants first. It can be used to feed cattle during all stages of production but may require protein supplementation in specific scenarios.
Younger growing animals and cows in the third trimester of pregnancy may require supplementation. It is also recommended to supplement cows that are less than a body condition score five as they need to gain condition for calving and re-breeding. Cows with a body condition score of five or greater do not likely need additional supplementation during early to mid-pregnancy while grazing corn stalks.
Although corn stalks may meet the energy and protein needs of certain livestock, a mineral and salt package needs to be provided. Corn residue is likely to be deficient in several of the minerals and vitamins. For any corn stalk questions, consult with your county extension agent and/or nutritionist prior to grazing.