Hay sustains cattle, but hay made from small grains also can contain dangerously high nitrate levels, a University of Nebraska specialist said.
While drought usually is the cause for high nitrate levels in hay made from small grains, normal precipitation this year doesn't mean nitrates won't be hazardous, said Bruce Anderson, NU Institute of Agriculture and Natural Resources forage specialist.
"Drought might be a major factor influencing nitrate content, but other factors also are important," he said.
Fertilization, cutting height, maturity stage at harvest, drying conditions and the small grain type all play a role in nitrate levels even if rain events are normal, Anderson said.
Nitrates poison cattle by converting to nitrite, which reacts with hemoglobin in the blood and blocks the cow's ability to use oxygen.
Symptoms of nitrate poisoning include brownish-colored blood, difficult and rapid breathing, muscle tremors, low tolerance to exercise, lack of coordination, diarrhea, frequent urination, collapse and death.
Oats have high nitrate levels most frequently, but wheat, rye and triticale also can be hazardous, he said.
The best way to make sure feed is safe for cattle is to test it, Anderson said. Farmers should take core samples from at least a dozen bales and have them tested in a laboratory. If some bales are known to come from areas most likely to produce high nitrates--such as droughty soils, heavily fertilized or manured areas or very young growth--most of the samples should come from those bales. Results should be used to determine if nitrate levels are safe or if the hay should be mixed with other, low-nitrogen feed.
"Don't risk cattle losses by assuming your hay is safe," Anderson said. "Test to be sure."
For more information on the dangers of nitrates in feed, consult NU Cooperative Extension NebGuide G74-170-A, Nitrates in Livestock Feeding, available at local extension offices and on the Web, at www.ianr.unl.edu/pubs/beef/g170.htm.