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Utilize Sorghums for Grazing Animals Prior to Frost

Above photo: Sheep grazing sorghum

Some forage producers and graziers may have considered a double-crop option after wheat. A Purdue forage specialist explained one of these options, and the importance of its utilization prior to a fall frost.

“If winter wheat is part of your farm enterprises, an immediate double-crop seeding of sudangrass, sorghum-sudangrass, or pearl millet after grain harvest should be considered if forage resource is limiting,” said Keith Johnson, Purdue forage specialist. “These crops can be grazed, made into traditional chopped silage, or ensiled as baleage.” He said that hay can be an option if an extended dry period after cutting occurs to get to a safe moisture content (less than 18 percent in large round bales).

“Consider brown midrib hybrids/varieties (BMR) if improved digestibility is ideal for the livestock being fed,” said Johnson.

If you plan to graze sorghum-sudangrass or sudangrass here in the waning weeks of the growing season, make sure to utilize those crops prior to the first fall frost to reduce the fear of prussic acid poisoning.

“Members of the sorghum family have a compound called dhurrin that will release hydrogen cyanide, commonly known as prussic acid, when plants are stressed by drought or frost,” said Johnson.

Although this scenario will be more common in southern Indiana, he cautions producers with Johnsongrass, a weed, in their pastures. “Historically, Johnsongrass was planted for forage purposes, but soon received the label of a prohibited noxious plant because of its ability to be where it wasn’t desired because of seed shatter and rhizomes,” said Johnson. “Being a sorghum, Johnsongrass has the potential to produce hydrogen cyanide and cause livestock death when plants are stressed.” He said that other desirable sorghums when stressed will produce hydrogen cyanide, too.

“Johnsongrass, when damaged by severe drought or frost, has the potential to produce prussic acid (hydrogen cyanide),” said Johnson. “Producers are encouraged to utilize sorghums before a frost occurs to reduce the possibility of prussic acid poisoning.”

“In the near future, dhurrin-free sorghums will be available for seeding as a result of Purdue University work conducted by Dr. Mitch Tuinstra’s research group, most notably Dr. Shelby Gruss,” said Johnson. “Unfortunately, Johnsongrass will remain to be a concern even when dhurrin-free sorghums are available.”

Find more information in the Purdue Extension publication AY-378-W, Managing the Prussic Acid Hazard in Sorghum, at

Find Johnson’s original article, which includes a related video, at:

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