By Randy Saner and Mary Drewnoski
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 lbs. 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 1 month. To calculate how much feed is available in each field you can use the cornstalk grazing calculator found at https://cap.unl.edu/livestock/tools/. However, in recent studies, the University of Nebraska-Lincoln has found high yielding corn (200 bu/ac 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. We suggest a 4 oz free choice mineral contains containing at least 300,000 IU per pound of Vitamin A, 4 to 5% phosphorus, 1500 to 2500 parts per million copper and 3000 to 5000 parts per million zinc.
Source : unl.edu