Can you graze cattle on a sudangrass or sorghum-sudangrass pasture after a freeze?

Sudangrass and other types of sorghum or sorghum-sudangrass hybrids are often planted for summer pasture. They are sometimes fed as greenchop, silage, or hay. Under certain conditions, livestock may develop symptoms of prussic acid poisoning if these forages are fed. Deaths occurring from prussic acid poisoning are usually caused by feeding on very young shoots or plants stunted by drought or frost. If plants are damaged by freezing, chewing, or trampling, then large quantities of emulsion along with hydrocyanic acid or prussic acid can be released in the leaves. Cattle and sheep are more susceptible than swine or horses since they are more likely to consume large quantities of the poison. The signs of poisoning appear suddenly, within 15 to 20 minutes, after animals consume the forage. The symptoms include staggering, labored breathing, spasms, and foaming at the mouth. In some cases, the animals die suddenly. Treatment must be administered quickly, which means contacting your veterinarian, to prevent death. Do not try to move cattle that have prussic acid poisoning as this will hasten complications because oxygen carrying capacity of the blood is compromised.

What precautions can you take? Poisoning is less likely to occur if animals have been fed grain or other forage before being turned onto the sorghum. Do not graze the crop after a frost if new shoots develop or if it is under two feet tall. Wait until the sorghum has wilted and dried (five to six) days before grazing. Don’t feed silage until three weeks after ensiling. For more information, contact your local Cooperative Extension office.