When lethal amounts are consumed, animals can die without visible symptoms of poisoning. Symptoms from smaller amounts include labored breathing, irregular pulse, frothing at the mouth and staggering.

University of Georgia Extension offers the following suggestions for farmers to help their cattle avoid prussic acid poisoning:

  • Remove cattle from fields containing johnsongrass until the first hard frost and when the grass is dry. The toxin usually dissipates within 48 hours.
  • Do not allow cattle to graze for two weeks after a non-killing frost.
  • Do not allow cattle to graze at night when frost is likely.
  • Allow hay to cure properly to remove the danger of prussic acid poisoning from hay containing johnsongrass.

Watch cattle closely if you have to leave them exposed to johnsongrass. Of course, you can't save a dead animal, but those displaying symptoms prior to death can be treated. A proprietary sodium nitrite-sodium thiosulfate combination can be administered and repeated once if necessary. It must be injected intravenously and very slowly. The dosage and method are critical, so keep a veterinarian's emergency phone number close by. Most animals that live two hours after onset of symptoms will recover.

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