Prevention of Nitrate Poisoning
Corn silage and sorghum/Sudan grass hay can accumulate
sufficient amounts of nitrates to poison livestock (particularly
ruminants). Nitrate accumulation in these forages occurs
most oflen in heavily fertilized fields and under drought
conditions. A diet consisting of greater tlian 1% nitrate
can potentially result in nitrate poisoning in ruminants.
Clinical signs of nitrate toxicosis occur when blood methemoglobin
concentrations are between 30 and 40%. The most common abnormal
signs are: dyspnea, weakness, ataxia and terminal convulsions.
Death occurs when blood methemoglobin concentrations
exceed 80 to 90%. Samples to submit when nitrate poisoning
is suspected are: feed, forage, hay, and water. From the
animals, frozen samples of plasma, urine, rumen contents
and vitreous and/or aqueous humor (or a whole eyeball) should
be collected and submitted for nitrate analysis.
Management suggestions for helping to prevent nitrate poisoning
include:
1. If possible, do not feed forages high in
nitrates.
2. If the forage is suspected of possibly being high in
nitrates, submit a representative sample for testing.
3. When harvesting suspect forages such as corn, raise
the cutter bar approximately one foot, since most of the
nitrate accumulates in the lower portion of the stalk.
4. Ensile the material and do not feed for at least three
weeks until the ensiling is completed. Ensiling will decrease
the total nitrate content. Be careful of potentially dangerous
nitrogenous gases produced by the ensiling process.
5. Drying does not appreciably decrease the amount
of nitrate in the forage. Therefore, even cured grass (sorghum
X Sudan hybrids particularly can accumulate large quantities
of nitrates) for hay can have a high nitrate content.
6. If feeding a suspect forage, also feed good quality
carbohydrate feed (approximately two pounds of grain per
450 Ib body weight).
7. Gradually introduce suspect feeds into the diet and feed
several times per day in small amounts rather than all at
once.
8. Young, stressed, and unhealthy animals are
more susceptible to nitrate poisoning.
9. Be sure that the nitrate concentration in the drinking
water is below a toxic level. Generally, water nitrate levels
of 45 ppm or less are considered safe.
- by Toxicology:
- Jennifer Harms, BS, Toxicology Technician
- Christina Wilson, BS, Assistant Chemist
- Robert Everson, PhD, Analytical Chemist
- Stephen Hooser, DVM, PhD, Toxicologist
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