Cornstalk residue is a good source of nutrition for the beef cow. When grazing cornstalks, we want to use about 15% of the residue. This 15% includes any remaining corn and 50% of the husk and leaf. Those parts are the most palatable and the highest quality nutrition for the cow.
For every bushel of dry corn, the husk makes up 3 pounds per bushel and the leaf makes up 14 lbs. per bushel. The highest nutrition out in the field is the corn that was left in the field. A cow’s intake and diet quality declines as she is left in the field. When cattle graze corn residue they select corn first, husk and leaf second, cob and stalk last.
When cows are forced to eat cob and stalk, they can’t meet their nutritional needs. A general rule of thumb is that for every 100 bushels of dry corn produced a cow can graze for one month. To calculate how much feed is available in each field you can use the corn stalk grazing calculator found at cap.unl.edu. However, in recent studies, we have found high-yielding corn (200 bushels/acre or greater) has less leaf and husk per bushel and that the quality is generally lower than lower yielding fields. We suggest reducing the grazing days by 10% in higher yielding corn hybrids. This can be accomplished by changing the utilization rate to 45% instead of 50% in the grazing calculator.
When grazed properly, pregnant cows can meet their energy and protein needs without supplementation when grazing corn residue. However, they do require supplementation of minerals and vitamin A. We suggest that a 4-oz. free choice mineral contains at least 300,000 international units per pound of Vitamin A, 4 to 5% phosphorus, 1,500-2,500 parts per million copper and 3,000 to 5,000 parts per million zinc.
However, corn residue, especially husk, is susceptible to losses from trampling and wind. Monitoring husk availability is a great way to ensure cows are receiving the nutrients they need. When they are hard to find, either move cows to a new field or start feeding a supplement. Bred and first-calf heifers have hinger energy and protein requirements and need to be supplemented. During mid gestation, 2-3 lbs. of distillers dried grains or 4-6 lbs. of modified distillers, and during late gestation, 3-5 lbs. of distillers dried grains or 6-10 lbs. of modified distillers grain, per day will meet their needs.
In conclusion:
• If high yields around 200 to 250 bushed yield, cut back to 40% utilization.
• Monitoring availability of husk in the field is a great way to gauge utilization.
• Heifers require supplementation with a protein and energy source.
• All cattle need access to a mineral source with vitamin A.
• If cows are losing weight supplement or move to another field. — Randy Saner, University of Nebraska–Lincoln Extension educator
