Plants grown in soils high in nitrogen but low in phosphorus and potassium tend to have high cyanide concentrations. Wait at least seven days after a killing frost before grazing to allow HCN to dissipate. Do not graze new growth or regrowth in sorghum or sorghum-sudan pastures. Feeding grain or hay before turning animals into pasture may reduce the rapid intake of forage and thus the amount of cyanide consumed. Animals do not develop immunity to cyanide, but they can detoxify low levels of cyanide.
Fresh forages have higher concentrations of prussic acid than silages or hay.
However, if the forage had extremely high concentrations of prussic acid before cutting or if the hay was not properly cured, dangerous levels of prussic acid can remain. If there is any doubt as to the level of prussic acid in a forage, suspect hays and silages should be analyzed before feeding. Guidelines Cattle are more susceptible to prussic acid poisoning than sheep. Horses can also be affected. Keep the following guidelines in mind when feeding forages such as sorghum and sorghum-sudan hybrids.