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Frosty weather brings with it concerns about prussic acid

10/11/2012

By STACY CAMPBELL

Special to The Hays Daily News

The questions have started about swathing failed grain sorghum and if prussic acid could be a problem. The short answer is no, as long as the hay properly is conditioned and cured or dried before baling, which you do anyway.

The confusion is prussic acid can be dangerously high after a freeze in the younger, more tender leaves and new shoots, "suckers" or tillers. Most losses of cattle occur when hungry or stressed animals graze young sorghum growth after a freeze.

Therefore, grazing immediately after a freeze can create problems of prussic acid poisoning in cattle. Waiting at least five days or until the frozen leaf tissue completely has dried out after a freeze before grazing is advised. Prussic acid does dissipate or leave the plant through ruptured plant cell walls from the freeze.

Plant species most commonly involved with prussic acid poisoning are forage and grain sorghums, Johnsongrass, shattercane, sudangrass and sorghum-sudans crosses. Hybrid pearl millet and foxtail millet generally are considered to not have high prussic acid concentrations.

Generally, any stress condition that retards normal plant growth can increase prussic acid content. Prussic acid is released when plant leaves physically are damaged by trampling, cutting, crushing, freezing, wilting or chewing.

For more information, call your local Extension office.

Stacy Campbell is Ellis County agricultural agent with Kansas State Research and Extension.