Iowa State University highlights management strategies to reduce prussic acid risk in sorghum forage

Iowa State University Extension and Outreach has released a new publication aimed at helping livestock producers manage the risks associated with prussic acid toxicity in sorghum forage. The document, titled “Management Strategies of Prussic Acid Toxicity in Sorghum,” offers practical guidance for safely incorporating sorghum into forage systems.

Sorghum is known for its fast growth and drought resilience, making it a dependable forage option, particularly in years with planting delays or inconsistent rainfall. “As weather extremes challenge consistent forage production, sorghum offers livestock producers a reliable, high-yielding alternative — especially during drought or delayed planting,” said Shelby Gruss, assistant professor and extension forage specialist at Iowa State University.

However, Gruss cautioned that sorghum also carries the risk of prussic acid (hydrogen cyanide) toxicity, which can be fatal to cattle. The risk is highest after frost events, during early plant stages, or when sorghum is over-fertilized with nitrogen. According to the university’s guidance, cattle can die within two hours of consuming toxic forage.

The publication outlines several strategies to mitigate risk, including adjusting grazing and harvest timing and opting for safer processing methods. “Silage and baleage production offer the safest choice for sorghum forage with high dhurrin accumulation,” Gruss noted. “Dhurrin content can be reduced by 50% or more through chopping and fermentation.”

Key recommendations include:

• Avoid grazing sorghum plants under 18 inches in height and monitor regrowth.
• Remove livestock from sorghum fields for at least one week following frost.
• Limit nitrogen fertilization to reduce toxin accumulation.
• Test forage when in doubt to confirm it is safe for feeding.