Crops in the sorghum family, including Green Graze and Johnsongrass, accumulate prussic acid in response to plant stress, which can be caused by drought, grazing, or frost. With the possibility of frost nearing, the chance of prussic acid poisoning increases.
Following a severe frost, avoid grazing for 14 days.
Farmers can also make hay out of frost-damaged Johnsongrass; the prussic acid disappears during the hay curing or ensiling process.
Contact your local Extension Office for more information.