FEEDING FACTS
The Dangers of Grazing After a Frost As fall weather gets here and the first frost of fall gets closer, anyone grazing livestock needs to pay attention to what type of grasses your animals are grazing and if there are any dangers associated with grazing those particular plants after a frost or freeze. Most of the plants we graze are perfectly fine. Bermudagrass and Bahiagrasses tend to be perfectly safe to graze as long as they are available. Fescue can actually get better after a frost than it was before. However, there are some plants, particularly those in the sorghum families, including Johnsongrass, or sorghum sudangrasses that are well-known for producing prussic acid in times of stress and especially after a frost. Prussic acid is a cyanide-based
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Cooperative Farming News
compound that is absorbed into the blood. It binds with hemoglobin and interferes with oxygen transfer. This causes asphyxiation and can kill an animal within minutes. Some of the symptoms of prussic acid poisoning are excess salivation, difficulty breathing, staggering, convulsions and collapse. These symptoms tend to happen rapidly and ruminants are more susceptible than other species because cud chewing and rumen bacteria increase the release of cyanide. When plants freeze, changes occur rapidly in their metabolism. Light frosts that stress the plant but do not kill it entirely are associated with prussic acid poisoning. Cyanide compounds are generally highest in
