Nitrate toxicity in drought-stressed corn
Extreme drought conditions create high nitrate levels in corn forages. This causes health problems in livestock, so have your corn tested before you feed it.
Radio interview source: Doug Shoup, Extension Crops and Soils Specialist, Kansas State University
Drought ruins pastures and forages for many livestock producers. Some turn to failed corn crops as a food source for their animals. However, feeding the wrong part of the plant can make livestock sick from nitrate poisoning.
Doug Shoup is an extension crops and soils specialist at Kansas State University. He says under normal conditions, nitrogen helps corn grow. But under extreme drought, the top part of the plant can't metabolize the nitrogen because of the lack of water. This results in high levels of nitrate in the lower leaves and stalk. If consumed by livestock, it can lead to asphyxiation.
"Excess nitrates will be converted into nitrites that react with the hemoglobin in the blood," he says. "Some of their membranes around their nose, and lips, and mouth will turn blue as well just from lack of oxygen."
Cattle and horses are more susceptible than sheep and goats. Symptoms of nitrate poisoning take several days to appear.
Shoup says it's impossible to tell just by looking at a plant whether or not it will be harmful if fed to livestock.
"The corn grain itself is not going to have a nitrate problem, it's mainly in the forage," says Shoup. "So if you're feeding hay or some sort of forage of failed corn, you can't see that in the plant, and it doesn't really go away, either, under a haying or grazing situation. So you actually have to take sections of the plant and send it off to a lab to get the most accurate test. They'll give you a reading back and tell you how high the nitrates are in that plant tissue that you sent off."
High nitrate forages chopped for silage are safer for livestock feeding. Another option is to blend them with other forages such as prairie hay or brome to dilute the total nitrates.
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