Farmers and livestock producers are being warned by Tim Evans, an associate professor of veterinary pathobiology and toxicology section head at the Veterinary Medical Diagnostic Laboratory at the Univ. of Missouri College of Veterinary Medicine, that drought-damaged corn plants can pose a risk to animal health.
“During severe drought conditions, corn plants, especially those heavily fertilized with nitrogen, can accumulate a chemical called ‘nitrate’,” Evans said. “This chemical can be very harmful to animals, especially cattle, if they eat corn plants or other vegetation containing too much nitrate. Eating plants with too much nitrate can cause damage to red blood cells, resulting in lethargy, miscarriage, and even sudden death.”
During normal conditions, corn crops typically absorb nitrate into only the lower 12-18 inches of the stalk, which does not have to be fed to animals, Evans said. But during severe drought conditions, high concentrations of nitrate can accumulate in the upper portions of the stalk that cattle and other livestock often consume.
Many naturally growing plants and weeds in grazing pastures can accumulate nitrate during drought conditions, as well, he added. These plants include many types of grasses and some weeds, which animals might be forced to eat because of limited pasture or hay available as forage for livestock.
Farmers should test the nitrate levels of their crops and pastures before allowing their animals to eat any of the plants, Evans suggests. Corn plants being harvested early for making silage, which generally contain lower concentrations of nitrate, should also be tested for nitrate before and after fermentation to determine the concentrations of nitrate being fed to cattle.
“Missouri farmers should definitely contact their local MU Extension offices for help in the preliminary stages of testing the nitrate concentrations in their crops,” Evans said. “MU Extension workers have their boots on the ground all across the state and are truly a valuable resource for farmers who are worried about their crops and livestock.”
High nitrate levels in plants are generally not a danger to humans, but only to ruminant animals, such as cattle, which eat very large amounts of plant material daily, Evans said.
