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Time To Graze Crop Residue
DR. TERESA L. STECKLER
SIMPSON, ILL.
Winter-feeding of the beef cows represents the greatest expense in most beef cow-calf enterprises. Of the winter ration, hay represents the largest portion of these winter-feeding costs. Harvested forages are expensive because there is a large investment in equipment, a large amount of labor to make and feed, and more than 50 percent of it is wasted by either poor storage methods or improper feeding practices, or both.
Therefore any opportunity to reduce the cost of harvested forages should be taken. Allowing cows to graze to meet their nutritional needs is much less expensive than delivering harvested forages to them. One great inexpensive option right now is crop residues.
Producers primarily will allow cattle to graze corn residue, but grain sorghum is also a good choice. Keep in mind that when grazing residue, cattle will select and eat the grain first, followed by the husk and leaf and finally the cob and stalk. Unless the corn field has experienced high winds causing a lot of corn to be left in the field or drought conditions result in small ears, there is usually less than a bushel of ear drop per acre. 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.
Cornstalks grazed shortly after harvest are higher in nutrient content than fields grazed 60 days after harvest. Ordinarily, dry cows will maintain body weight, and may gain weight, on corn and grain sorghum residue grazing programs when grain, husks, and leaves are available.
Do not force cattle to eat the cobs and stalks. Stalk fields are nutritionally adequate for most mature beef cows in mid-pregnancy and ordinarily, dry cows will maintain body weight, and may gain 0.5-1 pound per head daily, on corn and grain sorghum residue grazing programs when grain, husks, and leaves are available. Young animals or cows calving early in the winter would require about one-half pound of additional protein in the daily ration.
Before allowing cattle to graze corn and grain sorghum residue it may be prudent to scout fields to determine how much corn is there. Cattle will act like a vacuum and find every kernel of corn before moving on to the husk. If there is too much corn, moving cattle that are hungry to corn stalks with no prior rumen adaptation to starch can suffer from acute acidosis – a sudden drop in rumen pH caused by rapid grain overload that can lead to illness or death.
To prevent acidosis due to a large amount of leftover corn and/or to better utilize the residue, consider strip grazing. Strip grazing will prevent the cattle from gleaning the entire filed of corn and will force them to consume the leaves and shucks. Usually only a single hot wire is needed, but if calves are present be vigilant that they do not escape.
Stocking rate influences the amount of grain, husk, and leaf available per animal. The amount of grain, leaf, and husk available affect diet quality because they are highly digestible. Residue (leaf and husk) yield left in the field is related to corn grain yield. There will be about 16 lb dry leaf and husk per bushel of corn yield.
In a Nebraska study, an acre of stalks contained a total of 6,780 pounds of dry matter, including 5 percent corn grain; 21 percent cobs; 41 percent leaves and husks; and 33 percent stalks. Although these figures will vary by plant population, harvesting equipment and the grain yield, it is safe to assume that about two-thirds of the field will contain usable cattle feed. The carrying capacity of an acre of stalk fields is about 45 days for the average cow, but it may be less for larger cows.
Many grain producers are hesitant to allow cattle to graze corn fields. However, very few nutrients are taken by the grazing cow from the field. Nebraska workers found that a cow gaining 80 pounds will take only three-fourths of a pound of actual nitrogen from the field. But keep in mind that nutrients are also returned to the field in the form of manure and urine.∆
DR. TERESA L. STECKLER: Extension Specialist, Animal Systems/Beef, Mt. Vernon Extension Center, University of Illinois
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