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Nitrate or Prussic Acid Toxicity
Forages suspected of having toxic levels on nitrate or prussic acid should be sampled before grazing or feeding. Nitrate content of forages during hot dry weather may become high enough that production loss or death occurs in animals consuming them. Nitrate in itself is not very poisonous, however, when consumed in large amounts by ruminants, rumen micro flora reduce nitrate to nitrite, which is toxic. For this reason nitrates are not dangerous to monogastrics, such as swine as they are to ruminants. Symptoms of acute nitrate toxicity include salivation, vomiting, diarrhea, colic and frequent urination. Muscle tremor, weakness and loss of coordination are also observed. The mucous membranes are blue and blood becomes dark chocolate brown in color. Symptoms may appear ¼ to 4 hours after consumption and death occurs in 12 to 24 hours.
Practices that help prevent nitrate poisoning include:
1. Allow plants to mature before harvesting
2. Since most of the nitrate is in the lowest part of the stalk set cutter 12-18 above ground.
3. Ensiling usually eliminates about half of the nitrate.
4. Known nitrate-containing forages can be diluted by simultaneously feeding nitrate-free forages.
5. If consumption can be spread out over longer feeding period, mere total nitrates can be tolerated.
6. Ruminants can be conditioned to nitrates and then can tolerate higher doses.
7. Test suspected forages prior to feeding and care should be taken to collect representative samples.
Because nitrate levels are usually highest in the lower stalk, cut off the plant at found level when sampling.
Prussic Acid is a rapidly acting poison that may kill ruminant animals within fifteen minutes after forages containing it are consumed. The leaves and seeds of the plant contain most of the prussic acid. Young, growing plants are more likely to contain the poison than older, mature plants. Plants stressed by heat, drought or frost or making regrowth after grazing or mowing, are likely to contain prussic acid. Symptoms of poisoning include anxiety, restlessness, labored breathing convulsions and death. Mucous membranes usually are bright, cherry red. Things that may help prevent prussic acid poisoning include:
1. Plants that are grazed or green chopped should be near maturity or in the flower stage.
2. Plants used as hay should be mature and completely dried before baling.
3. Ensiling will release the cyanide, but hydro cyanic gas will be released and this gas may be deadly to man or animals. Prussic acid will dissipate if the sample is allowed to dry, so ship the sample immediately to a lab for testing.
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