Dale Watson
Commercial Agriculture Beef and Livestock Specialist
University of Missouri Extension




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Please send your comments and sund suggestions to Dale Watson, Commercial Agriculture Beef and Livestock Specialist, University of Missouri Extension, 111 N. Mason, Carrollton, MO 64633, call 660-542-1792, or send messages by e-mail to: watsond@missouri.edu.
For the Week of
September 17, 1998

Prussic Acid Poisoning

Each year concerns are expressed about the causes and effects of prussic acid poisoning.

Prussic acid poisoning occurs in ruminant animals that consume plants which contain high levels of hydrocyanic acid. Prussic acid poisoning occurs when high levels of hydrocyanic acid are present in very young and drought stressed, frost injured or wilted plants of the sorghum family. These include varieties of grain sorghum, forage sorghum, Sudan grass and Sudan grass hybrids and plants commonly thought of as weeds such as shattercane and Johnson grass. Other plants that need to be remembered for possible prussic acid poisoning include very young Indian grass and wild cherry.

Symptoms occur within a few minutes after the animal consumes plants containing high levels of hydrocyanic acid. Within the circulatory system prussic acid poisoning acts much like cyanide poisoning. Deep rapid breathing with excessive foaming from the nose and mouth are the first symptoms. These symptoms are followed by depression with severe difficult breathing and death within a few hours. Treatment must occur rapidly after the onset of symptoms if the animal is to be saved.

Preventing prussic acid poisoning is the best treatment. One management technique is to delay the grazing of sorghum plants until they are approaching maturity. If you plan to graze Sudan grass the recommendations are to graze after the plant reaches 15 to 18 inches in height. If hybrid sorghum or hybrid crosses are used for gazing these plants need to reach 28 to 30 inches in height. Do not permit animals to graze wild cherry trees which have fallen. Sorghums have the potential to cause hydrocyanic acid poisoning 7 to 10 days after frost. If you plan to graze plants of this nature is recommended to have the animals fully fed with dry hay before turning them into pastures of the sorghum family. This management method reduces the high intake effect of the sorghum plants when the animals are turned into grazing areas of this type. Plants will lose the hydrocyanic acid problem causing potential when the plants are permitted to dry and stored as hay. However, plants of this nature that have been fertilized with liberal applications of nitrogen have the potential of producing nitrate poisoning.

Remember that levels of hydrocyanic acid reduce with the drying or haying process and the potential for nitrate poisoning remains with the forage throughout the drying and storage process.

University of Missouri ExtensionDale's Country Trails - September 17, 1998
http://outreach.missouri.edu/agconnection/DCT/CT091798.html -- Revised: April 20, 2004