Corn residue: cheap grazing for cattle

Grazing corn can benefit both cattle and cropland.

by Eldon Cole, University of Missouri Extension

Grazing drought-dried corn and cornstalks offers cattle inexpensive, nutritious forage, say two University of Missouri (MU) Extension specialists.

Many corn and livestock growers turned to longtime MU Extension Livestock Specialist Eldon Cole to ask about grazing dried-up corn after persistent drought in southwestern Missouri this season.

Cole says damaged corn makes suitable grazing for cattle — with some restrictions and a commitment to timely moves to new pastures.

In late July, Cole visited Merle Schnelle, a row-crop farmer near Meinert in Dade County. Schnelle planned to let cattle graze 1 acre per day. Eighty of the 100 cows he planned to graze on corn were nursing spring calves. The other 20 would calve in the fall.

Schnelle provided Cole with details about his cornfield. Plant population was 25,000 per acre. The insurance adjuster estimated that grain yield would be only 4.5 bushels (bu.) per acre.

Schnelle set 36-inch-high single-wire fence run by a solar charger. Before placing the wire, he mowed an open lane for the hot wire by running a 25-horsepower tractor with a 6-foot belly mower across the 40-acre field.

Cows adjusted quickly to moving daily to fresh green corn. Cole says the herd seemed to thrive on the corn and left little waste.

One concern in grazing corn is the chance of increased nitrate poisoning during drought. Cole says it is wise to test for nitrates before grazing. For details, see the MU Integrated Pest & Crop Management article “Stalk Nitrate-N Test: A tool for evaluating nitrogen management practices in corn”.

Grazing cornstalks is good way to fill forage gaps
MU Extension Beef Nutritionist Eric Bailey says grazing cornstalks is a good, inexpensive grazing option to extend the grazing season and fill forage gaps.

Cows are selective grazers, choosing the highest protein and most digestible parts first, says Bailey. First, they will eat corn grain, leaves, husks and finally stalks.

By eating the higher-protein parts of the corn first, cows may need little additional supplements. Energy is not limiting during the first 30 days of grazing. Protein will be limiting after 30 days on the same field at 0.5 pound (lb.) of crude protein (CP) per cow per day. Consider herd needs as the needs of lactating and fall-calving cows or stocker calves may be greater, says Bailey.

Bailey uses a simple rule of thumb for quick estimates: Bushels per acre divided by 3.5 equals grazing days per acre for a 1,200-lb. cow. For example, if the field produced 150 bu. per acre, then it would provide enough residue for 42 grazing days (150 divided by 3.5).

The more accurate estimate is to factor in residue produced per bu. of grain. There will be 16 lb. of leaf and husk residue per bu. of grain. In a 150-bu.-per-acre crop, there will be 2,400 lb. of dry feed per acre. Assume 1 acre per cow per month and try to leave cows on the field less than two months, Bailey says. This estimate is more conservative than the previous one, but will keep cows from consuming the lowest-quality plant parts (stalks and cobs).

Some dry matter is lost to trampling or weathering, so assume 50% harvest efficiency, Bailey says.

Convenient portable fencing systems make strip-grazing easier now than in years past. By moving cows to the feed instead of taking feed to the cows, producers can save time and money.

A side benefit is that cows will return nutrients to the land in the form of manure. Another advantage is that cows will eat corn grain fallen on the ground, and this may reduce the amount of volunteer corn in a field the following year.

Bailey says grazing can also save producers money by avoiding shredding and baling costs. Sample and test bales for nutritional value. Test for protein and energy, and supplement as needed.

Studies from the University of Nebraska show that there is no negative effect of grazing on subsequent grain yield over a five-year period.

Bailey recommends the following resources from the University of Nebraska–Lincoln (UNL):

University of Missouri Extension