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.
A cow’s intake and diet quality decrease the longer 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 cornstalk grazing calculator found at cap.unl.edu/livestock/tools. However, in recent studies, the University of Nebraska-Lincoln (UNL) has found high-yielding corn (200 bushel/acre or greater) has less leaf and husk per bushel and the quality is generally lower than lower yielding fields. Based on this research, it is suggested to reduce the grazing days by 5% in higher-yielding corn hybrids. This can be accomplished by changing the utilization rate to 45% instead of 50% in the grazing calculator.
When grazing corn residue properly, pregnant cows can meet their energy and protein needs without supplementation. However, they do require supplementation of minerals and vitamin A. UNL suggests a 4-ounce free-choice mineral contains containing at least 300,000 international units per pound of Vitamin A, 4 to 5% phosphorus, 1,500 to 2,500 parts per million (ppm) copper and 3,000 to 5,000 ppm zinc.
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 husk is hard to find, either move cows to a new field or start feeding a supplement. Bred and first-calf heifers have higher energy and protein requirements and need to be supplemented. During mid gestation, 2 to 3 lbs. of dried distillers grains or 4 to 6 lbs. of modified distillers per day will meet their needs. During late gestation, 3 to 5 lbs. of dried distillers grains or 6 to 10 lbs. of modified distillers grains per day will be sufficient.
In conclusion:
• If high yields, around 200 to 250 bushels, cut back to 45% utilization.
• Monitor availability of husk in the field as a 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 and Mary Drewnoski, Nebraska Extension
