Beware
of Prussic acid poisoning
with Frosted Sorghum-Sudan Grass
Richard
Leep
Department
of Crop and Soil Sciences
Michigan
State University
Cellular
damage to sorghums and sudangrasses from frost,
wilting, bruising, drought, excessive soil nitrogen,
or deficiencies in soil phosphorus or potassium
can result in prussic acid poisoning in cattle.
Prussic acid poisoning consists of the following
sequence of events:
plant cells rupture and cyanic acid (HCN)
forms from cyanogenic glucosides;
cattle consume forage with elevated HCN levels; HCN is absorbed from the rumen; HCN binds to hemoglobin; asphyxiation and death occur. Poisoning is most likely after a frost when
animals consume the leafy regrowth.
Regardless of season, plants less than 18-24
inches tall should not be grazed.
Once
frozen, sorghum, sorghum sudan hybrids, or their
aftermath should not be pastured.
As long as the plants show any green color
they may be very poisonous.
Both frosted sorghum and sudan grass can
be best and most safely utilized by ensiling them
for at least two weeks before feeding. Normal ensilage fermentation safely eliminates
the poisonous HCN.
