Grazing crop residues can also be an inexpensive option for winter grazing. The University of Nebraska-Lincoln Beef Team offers some insight and research the get the most from this type of grazing.
When grazing residue, cattle will select and eat the grain first, followed by the husk and leaf and finally the cob and stalk. Because of this selection process, the cornstalk residue diet consumed could be very high in energy content (70 percent TDN) at first to low (48 to 52 percent TDN) at the end of grazing. Also, as the stocking rate (number of cows per acre) increases, the nutrient content of the residue declines more rapidly as the grain and husk are being removed at a much faster rate.
In the Midwest, weather records indicate the range in number of continuous grazing days for crop residue is 65-111 days. Weather can be the most important factor in successfully grazing crop residue.
Stocking rate influences the amount of grain, husk, and leaf available per animal. The amount of grain and husk available affect diet quality because both are highly digestible. The rate of decline in digestibility is affected by stocking rate, trampling, residue components available, and environmental factors. Stocking rate influences the quality of the diet consumed and, consequently, the animal performance.
Residue (leaf and husk) yield is related to grain yield, but hybrids obviously vary in this relationship. With high producing corn (irrigated or with ample rainfall) there will be about 16 lb. dry leaf and husk per bushel corn yield. We estimate 50% utilization of the leaf and husk, according to the beef specialists. Instead of remembering this equation, the university offers the "Corn Stalk Grazing Calculator" to help determine the number of acres at a certain corn yield needed for a certain number of cows. To run this spreadsheet, you will need Excel.
Do not force cattle to eat the cobs and stalks. Ordinarily, dry cows will maintain body weight, and may gain .5-1 pound per head daily, on corn and grain sorghum residue grazing programs when grain, husks, and leaves are available.
Their data would suggest that March calving cows that were protein supplemented and those that were not protein supplemented grazing similar corn residue fields were similar in reproductive performance even though protein supplemented cows weighed 23 more pounds pre-calving. However, cows in both groups had a BCS greater than 5.0 prior to calving.
Cows grazed from mid-November to about mid-February each year and stocking rate was determined using the grazing calculator mentioned above. Cows were about a BCS of 5 when they began the corn residue grazing period. Salt, mineral and Vitamin A supplements are recommended for all cattle grazing crop residues.