Nitrate poisoning

Attention! This is a potentially life-threatening condition for your Cow. Time is of the essence, contact your veterinarian immediately.

Nitrate Poisoning

Nitrate toxicity can occur in cattle from consuming pasture, hay, feedstuff, or drinking water which have high levels of nitrates. The factors responsible for nitrate accumulation in plants are mainly nutritional, environmental and fertilization.

Diurnal changes
Light intensity is inversely correlated to the nitrate content of plants. Diurnal changes in light intensity lead to a diurnal pattern of nitrate accumulation in plants. The nitrate content during the day is usually low, since it is when light intensity is at its highest. At night, when light intensity is at its lowest, is when nitrate accumulation is at its peak. Also, plants will accumulate more nitrates if they are in the shade or during cloudy, rainy days.

Nitrate accumulation varies with the season, with it being higher during the autumn-winter than in the spring.

Plant part
The nitrate content differs depending on the plant part. Usually the highest nitrate content is found in the petiole, followed by the leaf, stem, root, inflorescence, tuber, bulb, fruit, and seed with the lowest.

Stage of growth
Nitrate levels are usually highest in younger plants and decreases as the plant matures.

Plant species
Certain species of plants are able to accumulate higher amounts of nitrate then others, which are thus more toxic when combined with other factors causing elevated nitrate levels.

Rain following a drought
Plants that survive drought may have high nitrate levels for several days following a rain event.

The only method to determine if nitrates may be a problem is through testing. Nitrate poisoning can be rapidly fatal. When nitrate poisoning is suspected, a veterinarian should be called immediately to confirm the tentative diagnosis and to start treatment.


Muscle tremors
Frequent urination
Blue-brown discoloration of mucosal membranes
Increased heart rate
Frothing at the mouth
Difficult and rapid breathing
Sudden death


  • History
  • Clinical signs
  • Physical exam
  • Laboratory tests


Methylene blue : (1 to 4% solution at the rate of 2 g per 500 lb of body weight) injected intravenously to convert methemoglobin to hemoglobin


  • Periodic testing of pasture and drinking water for nitrates
  • Don't apply fertilizer to pastures currently occupied by cattle
  • Walk pastures for nitrate-accumulating weeds


If caught early enough to be able to administer treatment.

Article Reference

Risk Factors

  • Drought
  • Fertilizer application
  • Nitrate-accumulating Weeds
  • Hay
  • Pasture grass

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