Duane Dailey
Senior Writer
573-882-9181
DaileyD@missouri.edu
August 14, 2003
Drought corn can make cattle sick if whole plant
is chopped for forage; nitrate testing recommended
The only way to know if the feed is safe is to have a quantitative test for nitrate content made by a certified forage-testing lab, the specialists advise. Nitrates can be converted into nitrites in the cattle rumen, or stomach. Nitrites block the oxygen-carrying capacity of the blood, which can be fatal.
"Grazing the corn fields offers a better alternative than chopping the crop and hauling it to the cow herd," said Rob Kallenbach, MU forage specialist.
"The first reaction is to chop the drought corn and feed it to livestock," said Craig Roberts, MU forage specialist. "When pastures run short, farmers turn to the grain fields for feed. But corn that has stopped growing because of lack of water may accumulate nitrates in the stalks."
Nitrates at levels of more than 15,000 parts per million (ppm) in feeds are considered toxic. Levels as low as 2,500 ppm must be fed with caution.
Test results returned from the lab will contain instructions on safety levels and feeding instructions, the specialists noted.
Forage with nitrate should be diluted with other feeds. Grain supplements with added Vitamin A also help.
The problem occurs when water from rain or subsoil moisture is restricted in an actively growing corn plants. In normal weather, corn plants extract nitrogen from the soil and convert it into energy to store in the kernels on the cobs. When the process slows, nitrates concentrate in the plants, particularly the stalks, before it reaches the ears.
The bottoms of cornstalks are most likely to contain the highest concentrations of nitrates, Kallenbach said. Any feeding system should avoid the lower stalks in particular, he added.
"Danger of nitrate accumulation occurs in almost every drought," Roberts said.
Some 36 counties in northwest and western Missouri are on a drought list forwarded by Missouri Gov. Bob Holden to the U.S. Department of Agriculture for assessment as a drought disaster area.
When cornstalks are harvested as "green chop," a process similar to cutting corn for silage, the high-nitrate stalks are mixed with the leaves that have low levels of nitrate.
Kallenbach says grazing the cornfields offers a safer alternative than making green chop. "Given a choice, the cows will eat the leaves and ears, which are less likely to have high nitrate levels. They will eat the stalks only when no other feed is available."
Farmers using grazing should introduce the drought-stressed corn to the cattle slowly over a week to 10 days. "Cattle can acclimate to withstand higher nitrate levels if feed is introduced over time," Kallenbach said. Calves and pregnant cows are most susceptible.
Farmers in Nebraska, who have years of drought experience, perfected the corn-grazing technique.
A strip of the cornfield is separated off with a portable electric fence to provide about three days of grazing, Kallenbach said. Grazing should be watched closely, and the fence should be moved forward in the field when the leaves and ears have been grazed but before cows begin eating the stalks.
A farmer on an all-terrain vehicle (ATV) can quickly install portable posts and string a single-strand electric wire across a cornfield. A portable electric charger powers the wire.
The ATV knocks down a strip of corn, which allows cows to see the new portable electric fence in the cornfield. "A lot of feed can be set off with about $200 worth of fencing supplies," Kallenbach said.
The grazing system works best on fields with a permanent perimeter fence. Stock water source must be available for grazing livestock.
Other crops, such as milo and sorghum-sudangrass, can accumulate nitrates in drought also.
Details on nitrate toxicity are contained in MU Guide, G4661, "Warm-Season Annual Forage Crops," written by Roberts and Kallenbach. The publication is available at University Outreach and Extension Centers, on the Internet at http://muextension.missouri.edu/explore/ or with credit card at 1-800-292-0969.
Source: Craig Roberts (573) 882-2801; Rob Kallenbach (573) 884-2213
| Return to Current News Releases | |
|
College of Agriculture Food and Natural Resources
AgEBB |