Grazing standing corn eliminates the costs of harvesting, transporting, drying, and storing grain. Expenses for cutting stalks for hay or chopping silage also are avoided. Plus, letting cattle do the harvest eliminates yardage expenses, manure hauling, and feed processing and handling.
After a brief learning period, cattle will preferentially graze corn ears if any have developed. Drought-damaged corn may not have many ears, but if much grain has developed, the cattle first need to adapt to a higher grain diet before grazing corn begins. Otherwise, acidosis or other digestive disorders could develop.
Cross-fencing and strip-grazing is needed to minimize trampling waste. Give cattle access to no more than a two-day supply of fresh corn at a time; a one-day supply is even better, especially for younger, growing cattle. Dry cows might do fine if moved just twice each week.
Electric fence is used most commonly for cross fences, but animals must be trained to respect these fences before entering the corn field. Driving over a strip of corn with a tractor, pickup, or four-wheeler before placing the fence in the strip makes it easier to set up the fence and visually alerts the cattle that the fence is nearby. Constructing multiple strips ahead of time provides a catch area if the original fence fails to keep animals in the desired smaller area.
Allotting per Cow Feeding Area
Determining how much area to give the cattle, especially in the first strip, can be challenging, but it need not cause serious mental anguish because adjustments are readily made in the size or time spent grazing the next strip. As a starting guide, each acre of standing corn that is about 6 feet tall and tasseled should provide enough grazing for about 100 cows for one day. In other words, provide 435 square feet of standing corn for each cow for each day of grazing in the first strip. Observe animal behavior and amount of grazable corn available each day, as well as in-field variation, to determine whether to increase or decrease the area allotted with each new grazing strip. Do not bother with back fences to simplify animal travel back to water.
Dry cows may become fat and over-conditioned grazing standing corn, especially if grain is present. Even without grain, barren stalks can be surprisingly high in nutrient concentration because protein and energy that normally would have been transferred to the grain has instead been stored in the stalk and leaves. Diets containing crude protein exceeding 8% and TDN of 55% are usually expected.
Standing corn can be limit-fed to stretch the supply and/or to minimize over-conditioning by reducing the area allotted to the cows and forcing them to eat more of the lower quality stalks. However, nitrate concentration may be high in the lower portion of the corn stalks. Before forcing animals to consume this part of the plant, test the stalks for nitrates and then manage accordingly. In addition, limit-feeding can cause animals to remain hungry even when they have consumed sufficient protein and energy to meet their needs. Behavior problems can occur, including increased pressure on fences. More strands of wire, higher electric voltage, or providing free choice access to poor quality hay or straw may be needed to avoid problems.
Instead of grazing standing corn, corn can be windrowed first and then cattle can be allowed to graze the windrows. This may simplify construction of fences and determination of area to be allotted. Trampling waste also can be reduced. However, if cattle do not utilize all of the corn in the windrows, the remaining residue might cause problems for planting crops next spring. Also, residue remaining after grazing will be concentrated in the windrows, which may not meet residue requirements for conservation purposes, compared to grazing standing corn.
The lower portion of corn stalks may be high in nitrates. If feeding, test corn stalks for nitrate and manage accordingly.
Source: Dr. Bruce Anderson