prussic acid and nitrate testing
TRANSCRIPT
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Forage Nitrate and Prussic Acid Screening Tests
Shelby Filley Regional Livestock and Forage Specialist
Oregon State University Extension Service
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Substances that can accumulate in certain forages and cause poisonings in livestock.
Nitrate Accumulators (pigweed, Johnsongrass, Sorghums, .)
Prussic Acid (Sorghums, Johnsongrass)
This presentation reviews the toxins, animal response, and two testing options.
Nitrates and Prussic Acid
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Nitrates are a normal part of plant metabolism. However, stressful growing conditions can lead to abnormal levels.
Nitrate absorbed by plants Reduced to nitrite Reduced to ammonia Used in amino acid formation Ends up as plant protein
Nitrate metabolism in Plants
NO3-
NO2-
NH4
AA
Protein
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Nitrate (NO3) —› Nitrite (NO2) ——› Ammonia (NH3) ——› Amino Acid ——› Protein
Too much nitrate, nitrite builds up, is absorbed, causes hemoglobin to be converted to methemoglobin, which is unable to transport oxygen.
Nitrate Metabolism in the Rumen
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Oxygen deprivation causes a bluish color of the mucous membranes of stricken animals.
The blood is chocolate-brown in color due to methemoglobin formation.
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Acclimate to nitrate level Older animals less sensitive Handle calmly
Animal Handling
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Dhurrin is a cyanogenic glycoside in plants of the Sorghum genus
Dhurrin is broken down with cytosolic enzymes upon plant damage (wilting, drought, frost, trampling, etc)
Prussic Acid
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Prussic acid (hydrocyanide, HCN) is released can build up in plants
Hydrocyanide interferes with the ability of animal cells to receive oxygen from the blood.
Prussic Acid
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Sample Collection
Nitrate Test – stems and new growth
Prussic Acid Test – collect leaves
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Microwave oven Coffee grinder Pencil scale
Nitrate Test Dry, grind, and weigh the sample
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Nitrate Test Soak sample in water for 30 min
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Check for color reaction and compare strips to chart of nitrate concentration
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With bag partially closed, use scissors to cut leaves into pieces
Cut a short piece of the Cyantesmo test paper and add to the bag
Close the bag Read the test strip
within 5 minutes
Prussic Acid Test Sample processing
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Prussic Acid Sample incubation
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Positive Control – choke cherry
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One of the 6 fields tested showed elevated levels of prussic acid (slight positive)
None of the 6 fields tested showed elevated levels of nitrates
Results
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Easy to conduct and can be done with items commonly found on the farm
Conclusions: Field Tests…
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We learned more Producers have testing options
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Safe? Field tests said yes. Lambs agreed
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Improved confidence in grazing forages
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Prussic Acid and Nitrate Poisoning Fact Sheets. Oklahoma State University.
Prussic Acid and Nitrate Testing Bob LaValle, Oklahoma State University Paul F. Vendrell University of Georgia
References