Graze Unharvestable Corn Fields

FARGO - Oct 29/04 - SNS -- Allowing cattle to graze corn fields which will not be harvested can be an efficient way to extra fed value from those fields, argues J.W. Schroeder, North Dakota State University Extension dairy specialist.

"Normally, we talk about adjusting harvest or expected losses, but in today's situation, this really doesn't apply," Schroeder said. "Rather, many want to know the salvage opportunity of that immature corn. . . However, grazing efficiency must be considered

"Animals will waste or trample some feed. Typically, 60% to 90% grazing efficiency can be achieved. Grazing efficiency increases when livestock have a shorter time to feed. Ideally, livestock should be fed only what they can consume in one day, which limits waste due to trampling. However, feeding rates of up to three days of grazing corn at one time have been achieved with higher waste losses, but less labor."

If you do not have a home use for corn forage or don't have a corn forage sales contract, then a crop insurance adjustment or other cash settlements should be seriously evaluated. If you do have a market for immature corn forage, green chopping is probably the best risk alternative.

Direct grazing has a low animal-use risk, but potentially a large field deterioration loss risk. Ensiling very wet corn has both a risk-cost outlay with a high risk of producing poor quality silage. "Feed represents 50% to 70% of the total cost of production, so, as a producer, you try to reduce that cost," Schroeder says. "For many producers, grazing may be the only option left this late in the year."

Cattle can get significant nutritional value from the direct grazing of immature corn plants, standing or lodged. Limitations include adequate fencing, water availability and the fact that downed plants will be further trampled by grazing. This will result in increasing amounts of deterioration, loss in dry matter when grazing and loss of nutrient quality.

In most instances, corn is strip-grazed, and livestock are allowed only enough forage for two to three days by utilizing an electrified temporary fence. The fence should have a minimum of two strands with temporary posts placed about 30 feet apart. Two strands are recommended to prevent livestock from reaching through or over the fence and to prevent the fence from grounding out if a corn stalk falls over the fence. For the fence row, corn rows are typically mashed down with a four-wheeler placed in the path of the swather.

The height of the corn needs to be evaluated when setting up the fence. Livestock can knock the corn down as they move through the paddock. This could short out the fence and make controlling the cattle difficult. Allow enough room so that falling corn stalks cannot reach the fence.

To help control livestock, corn should be perpendicular to the grazing line so that the animals can move into the row easily to minimize trampling. A good fence energizer that is adequately grounded is a requirement to prevent livestock from crossing the line and wasting corn in the rest of the field.

Livestock generally do a good job of cleaning up the grazing area. Producers should monitor their fields. If the livestock are not cleaning up the area being grazed, including the corn stalks, too much feed is being allotted and the grazing area should be reduced. Livestock commonly prefer to graze the leaves and grain first, leaving the corn stalks for last.

The rumen of beef and dairy animals develops at around 400 to 500 pounds. A fully functioning ruminant animal will consume 2.5% to 3% of its body weight in dry-matter feed per day. A 1,000-pound beef cow or replacement heifer will consume 2.5% to 3% of its body weight or about 25 to 30 pounds of dry-matter feed per day.

Assume that you have a 30-cow beef herd with an average weight of 1,000 pounds each. How large a grazing area do they need per day? Assume a mature corn field with 12,000 pounds of dry matter per acre, 75% grazing efficiency, 12% protein and 24,000 plants per acre. A good corn field can yield 20 tons of wet corn silage at 70% moisture (30% dry matter) or 12,000 pounds of dry matter. Adjust yields based on your field stand.

The daily pounds of dry matter required are equal to the number of animals multiplied by their average weight multiplied by the feeding rate as a% of their body weight. In this case, the number of cattle (30) is multiplied by their average weight (1,000 pounds) multiplied by their feeding rate as a% of their body weight (3%). A total of 900 pounds of dry matter is required daily for the 30 head of cattle.