July 13, 2004
Nitrate and Prussic Acid Concerns Elevated in Dry Areas
Cattle and sheep producers in dry areas of North Dakota should be aware of the increased likelihood of nitrate and prussic acid poisoning, says Chip Poland, Extension livestock specialist at the North Dakota State University Dickinson Research Extension Center.
Most cases of nitrate poisoning in North Dakota occur due to the consumption of environmentally-stressed oats, corn and barley. However, a number of other plants can also accumulate nitrate, including sudangrass, sorghum-sudan hybrids and pearl millet.
Not all drought conditions cause high nitrate levels in plants. Some moisture must be present in the soil for plants to absorb and accumulate nitrate. In plants which survive drought conditions, nitrates are often dangerously high for several days following the first rain until top growth can assimilate the excess. “Once accumulated, nitrate doesn’t dissipate rapidly without this growth,” Poland says.
Other weather conditions including frost, hail and low temperatures can also cause nitrates to accumulate and become toxic.
“Prevention of nitrate poisoning is best achieved by controlling the type and quantity of forage offered to livestock,” says Charlie Stoltenow, NDSU Extension veterinarian. “Avoid forages with potentially toxic levels of nitrate, and dilute forages with marginal nitrate levels with feeds low in nitrate. When grazing, feed dry roughage first to reduce the amount of affected plants ingested by hungry animals.”
When in doubt, Stoltenow recommends that feeds and forages be analyzed for nitrate before feeding or grazing.
Interpreting laboratory results can be challenging. “Producers must be aware that nitrate can be expressed as parts per million (ppm) or percentages, as well as in levels of NO3, NO3-N or KNO3,” Poland says. For help understanding the differences in acceptable levels, Poland advises producers to contact their local Extension agents.
Most North Dakota nitrate reports are expressed in NO3-N. The general recommendations for this nitrate are 0 – 1,500 ppm, generally considered safe for livestock; 1,500 – 4,500 ppm, mix, dilute, limit feed forages in this level; greater than 4,500 ppm, don’t feed, potentially toxic.
Prussic acid poisoning is also associated with drought conditions. Prussic acid levels increase significantly following a drought ending rain or a killing frost.
Follow these guidelines when looking at sorghum and sorghum-sudan hybrids:
For more information, contact Poland at (701) 483-2078 or Stoltenow at (701) 231-7522. To submit samples for nitrate and prussic acid analysis, contact the NDSU Veterinary Diagnostic Laboratory at (701) 231-8307.