What is in this article?:
- Johnsongrass, frost can be deadly to grazing cattle
- Cattle can die without visible symptoms of poisoning
- Johnsongrass, which can be found in pastures, can produce toxic levels of prussic acid, especially when stressed during cold temperatures and can then poison cattle.
- Prussic acid is one of the most potent toxins in nature.
- Remove cattle from fields containing johnsongrass until the first hard frost and when the grass is dry. The toxin usually dissipates within 48 hours.
A WET SUMMER set the stage for abundant johnsongrass in Georgia pastures. Cattlemen need to watch pastures near or after frost because this grass when stressed by low temperatures can turn toxic to cattle.
When the first frost hits, beef producers should be concerned for grazing cattle if the field contains johnsongrass. Cattle may suffer from prussic acid poisoning caused by this grass.
In normal years producers don't have to worry about this problem, but Georgia experienced a lot of rain this summer. Repeated grazing by cattle prevents johnsongrass from getting established. But the abundant rainfall may have caused some situations where the grass grew faster than the cattle could eat it. It is also prevalent in many hay fields, and some farmers may allow cattle to graze those fields this fall.
Cyanide-producing compounds in living plant cells are converted to prussic acid when cells are crushed or otherwise ruptured. The prussic acid potential of plants is affected by species and variety, weather, soil fertility and stage of plant growth. Plants of the sorghum group like johnsongrass and leaves of wild cherry trees can produce toxic levels of prussic acid, especially when stressed during cold temperatures.
Prussic acid is one of the most potent toxins in nature. As ruminants like cows and goats consume plant materials containing cyanide-producing compounds, prussic acid is liberated in the rumen, absorbed into the bloodstream and carried to body tissues where it interferes with oxygen usage.