Grazing or feeding green sorghums, sudangrasses and sorghum-sudangrass crosses to cattle can be a bit worrisome because of the threat of prussic acid poisoning. This risk is most evident when the plant is at a young, dark green growth or regrowth (less than 18 to 24 inches) and the danger increases just after a frost.
"However, they can be safely grazed a few weeks after freezing if there is no substantial regrowth," says Dan Undersander, professor of agronomy with the University of Wisconsin-Extension.
Regular sudangrass contains the least amount of prussic acid, while sorghum-sundangrass is more acidic and sorghum has the most risk of poisoning.
Undersander recommends mixing sorghum or sorghum-sudangrass with other feeds to reduce the danger of prussic acid poisoning. Here are the other recommendations Undersander lists when feeding these forage types:
· Silage. "Sorghum and sorghum-sudangrass silage is generally safe for feeding. Although it may have contained toxic levels of prussic acid when harvested, while in storage much of the poison escapes as a gas during fermentation and when being fed. However, as a precaution, do not feed new silage for at least three weeks after harvesting and storing."
· Hay. "The prussic acid content of sorghum and sorghum-sudangrass hay decreases as much as 75 percent while curing and is rarely hazardous when fed to livestock. Hay stored for two or more months gradually losses all its cyanide potential."
· Greenchop or grazing. "Do not graze sorghum or sorghum-sudangrass hybrids following a series of light frosts, as the potential for poisoning increases for a period of time after frosts. Allow seven to 10 days after a light frost before feeding greenchop or grazing. Do not green-chop graze sorghum or sorghum-sudangrass hybrids following a killing frost until the plant has dried, approximately seven days. Do not graze hungry livestock on sorghum or sorghum-sudangrass hybrids. Poisoning potential increases with the amount of high-risk forage consumed."
For more information on feeding sorghum or sorghum-sudangrass click here.