July 3, 2002

Watch Nitrate Levels in Drought-Stressed Forages

Livestock nitrate poisoning could become a problem as dry conditions in parts of the region are forcing some producers to consider grazing or haying small grains, according to a North Dakota State University livestock specialist.

"Plants that have been stressed by drought accumulate nitrate," explains Greg Lardy of the NDSU Extension Service. "Nitrate isn't toxic, but it is converted into nitrite during digestion. And nitrite is toxic." Once in the bloodstream, nitrite eliminates the blood's oxygen-carrying capacity and affected livestock die from a lack of oxygen.

"Most nitrate poisoning cases in North Dakota occur with drought-stressed oats, corn and barley," Lardy says. "But sudangrass, sorghum-sudan hybrids, pearl millets and some other plants can also accumulate nitrate." Plants that have been fertilized usually have higher nitrate concentrations.

Signs of nitrate poisoning include dark brown blood, labored breathing, noisy breathing, excessive salivation, bloat, tremors, inability to rise, coma and death. Females may abort offspring because the fetus doesn't get enough oxygen.

Poisoned animals can be treated by intravenous injections of methylene blue, Lardy says. Commercial preparations intended for treating prussic acid poisoning only should not be used to treat nitrate poisoning.

"It may be best to consult a veterinarian to confirm your diagnosis and to prescribe treatment," Lardy says. Likewise, extension agents and veterinarians can offer advice on how to analyze and manage feeds that pose potential nitrate problems.

"The best prevention is to control the type and quantity of forage offered to livestock," Lardy says. "Avoid forages with high levels of nitrate or dilute them with feeds and forages low in nitrate." When grazing, feed a dry roughage first to reduce the amount of affected plants ingested by hungry animals. Sheep and cattle are more susceptible to nitrate poisoning than other species because the microbes in their digestive tract convert the nitrate to nitrite.

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Source: Greg Lardy (701) 231-7660, glardy@ndsuext.nodak.edu
Editor: Tom Jirik (701) 231-9629 , tjirik@ndsuext.nodak.edu