Nitrate and Prussic Acid
Poisoning
Floron C. Faries, Jr. DVM, MS
Professor and Extension Program Leader
for Veterinary Medicine
Texas Cooperative Extension
Texas A&M University
Nitrate in All Forages
 Under growing conditions of moist soil
 In plant nitrate converted to protein
 In plant nitrate does not accumulate
 In rumen nitrate converted to protein
 Under no growing conditions of stress
 Weather, physical damage, heavily grazed

In plant nitrate accumulates
 In rumen high nitrate converted to nitrite
 In blood high nitrite is poison
 Nitrite poisoning
 Blood cannot carry oxygen
 Death by asphyxiation
 Fresh or dry forage
 Johnson Grass
 Sudan
 Sorghum
 Sudan-Sorghum
 Wheat
 Oats
 Rye
 Ryegrass
 Bermuda
 Fescue
 Weather
 Growth cease/nitrate accumulates
 Cold
 Hot
 Cloudy
 Shade
 Physical damage
 Growth cease/nitrate accumulates
 Heavily grazed
 Nitrate in lower stems and roots
 >1% nitrate of ration
 (>100 PPM)
 Energy feeds

> Conversion
Prussic Acid in Stressed Forages
 Under growing conditions of moist soil
 In plant prussic acid does not accumulate
 Under no growing conditions of stress
 Drought, hot, frost, freeze
 In plant prussic acid develops
 In rumen high prussic acid converted to cyanide
 In blood high cyanide is poison
 Cyanide poisoning
 Blood cannot carry oxygen
 Death by asphyxiation
 Fresh forage
 Johnson Grass
 Sudan
 Sorghum
 Sudan-Sorghum
 Weather/Damage
 Frost wilt winter
 Hot dry summer
 3 days
 New growth
 10 days
 Hay fill