NDSU Extension - Griggs County


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August 3

The Extension Connection

By Megan Vig

                Nitrate poisoning is a topic that comes up during this time of the year.  The majority of nitrate poisoning cases in North Dakota occur with drought-stressed oats, corn and barley.  However, a number of other plants also can accumulate nitrate.  Common crops known to accumulate nitrates include barley, corn, flax, millet, oats, radishes, rape, rye, soybean, sorghum, sudangrass, sugar beets, sweetclover, turnips, and wheat.  Common weeds known to accumulate nitrates include Canada thistle, dock, jimsonweed, Johnson grass, kochia, lambsquarter, nightshade, pigweed, Russian thistle, smartweed, and wild sunflower. 

The abnormal accumulation of nitrate in plants is influenced by various factors, such as moisture and soil conditions, and type of plant.  Plant stresses, such as drought, are associated with increased levels of nitrate in plants.  Further, soils high in nitrogen readily supply nitrate to plants; acidity, sulfur or phosphorus deficiencies, low molybdenum, and low temperatures are known to increase nitrate uptake by plants.  Stage of plant growth also affects nitrate levels.  Nitrate decreases as plants mature.  Young plants have higher nitrate concentrations than mature plants.  However, mature plants still can have excessive nitrate concentrations if environmental and soil conditions are favorable.

                Water may also be a source of toxic levels of nitrate for livestock.  Water may become contaminated by fertilizer, animal wastes or decaying organic matter.  Shallow wells with poor casings are susceptible to contamination.  Marginally toxic levels or nitrate in water and feed together may cause nitrate toxicity in animals.  Remember to consider both sources of nitrates.

                Signs of nitrate poisoning are related to the lack of oxygen in the blood.  Cattle and sheep are more susceptible to poisoning than nonruminant species because microbes in their digestive tract favor the conversion of nitrate to nitrite.  Acute poisoning usually occurs from a half hour to four hours after consuming toxic levels of nitrate.  Onset of symptoms are rapid and include the following: bluish/chocolate brown mucous membranes, rapid/difficult breathing, noisy breathing, rapid pulse (150+/minute), salivation, bloat, tremors, staggering, dark “chocolate-colored” blood, weakness, coma and death.  Pregnant females that survive nitrate poisoning may abort due to lack of oxygen to the fetus.  Abortions generally occur approximately 10 to 14 days following exposure to nitrates. 

                Prevention of nitrate poisoning is best achieved by controlling type and quantity of forage offered to livestock.  Avoid forages with potentially toxic levels of nitrate or at least dilute them with feeds low in nitrate. When in doubt, have feeds and forages analyzed for nitrate before grazing or feeding them.  If you have forages in the field that you would like to check to see if nitrates are present, please call the Extension Office at 797-3312 to arrange for a nitrate quiktest.  The results of the quiktest are qualitative, that is the test will read as yes or no that nitrates are present.  The best option would be to check and if the quiktest is positive, to send a sample in to be quantitatively tested.  Therefore, you will know exactly how much nitrate is present.  The quiktest has its testing limits but is still a helpful option for a quick, qualitative test.  Source: Nitrate Poisoning of Livestock NDSU Extension publication V839.

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