Farms.com Home   News

Watch Cattle Closely As Risk Of Prussic Acid Toxicity Increases During Drought, After Rains

Both summer and fall are important times for ranchers to keep an eye on cattle that graze where Johnsongrass is present, due to the risk of prussic acid toxicity.

Clark Roberts, manager of Noble Research Institute’s Coffey Ranch at Marietta, Oklahoma, says that drought conditions put him on high alert for two reasons.

“Anything that physically stresses Johnsongrass, such as drought in summer or freezing in the fall, can increase the amount of prussic acid in this invasive forage plant,” he says. “Secondly, with rain after drought, or warm temperatures after a frost, the fresh, green growth is one of the first things the cows will go after. That’s the danger, because those young leaves are higher in prussic acid.”

Prussic acid, known as hydrocyanic acid or cyanide, can form in plants in the Sorghum genus in different concentrations, depending on the species. Johnsongrass, grain sorghum and sorghum almum (Columbus grass) are all on the high end. As Roberts explained, the prussic acid, which can be fatal, is more concentrated in the leaves, especially younger leaves in the upper part of the plant, and more so during rapid regrowth after drought or frost injury.

Roberts manages cattle and sheep, focusing on applying the six soil health principles. He says there are steps one can take to try to prevent ruminants from ingesting too much Johnsongrass when it is in highly toxic stages. They include:

  1. Grow and offer a diversity of forages.
  2. Don’t turn animals out to graze areas with Johnsongrass after mowing, haying, or grazing when the plants are regrowing after stress from drought or freezing until the plants are at least 18 to 24 inches tall.
  3. Be sure animals are not hungry when first grazing a new field with the potential of prussic acid ingestion. Turn them out in late afternoon or feed some hay first.
  4. Be aware that warm season cover crop mixes may contain sorghum, which also poses a prussic acid toxicity risk.
  5. Keep cattle away from roadsides or bar ditches that have fresh, ungrazed Johnsongrass growing.
  6. Watch your animals closely in each new grazing area. Symptoms of prussic acid poisoning can occur within 5 minutes of eating affected forage, and death can occur in 15 minutes. Clinical signs include muscle tremors, increased respiration rate, excess salivation, staggering, convulsions and collapse.
  7. Remove all cattle and sheep to a new pasture as soon as any herd mate shows signs of prussic acid toxicity and contact a veterinarian.

“It also helps to have diversity so the cattle can select other forages other than Johnsongrass to graze,” he says. “Plus, I can observe my animals every day and that’s going to be especially important this year.”

PHOTOS

CROP

Prussic acid can form in Johnsongrass and other plants in the Sorghum genus.

CROP

Ranchers can take steps to try to prevent ruminants from ingesting too much Johnsongrass when it is in highly toxic stages.

CROP

Clark Roberts moves a bull on Noble Research Institute’s Coffey Ranch.

 

Click here to see more...

Trending Video

CEOs of the Industry – Rob Brenneman, CEO of Brenneman Pork

Video: CEOs of the Industry – Rob Brenneman, CEO of Brenneman Pork

“From Pork Production to Performance Nutrition: A Candid Conversation with One of the Industry’s Most Unconventional Thinkers”

CEOs of the Industry, we sit down with Rob Brenneman, the visionary behind Brenneman Pork, for an unfiltered, in-depth conversation on leadership, survivability, nutrition, and the future of pig farming.

Rob shares how a deep-rooted commitment to **health—both animal and personal—**drives his philosophy and decision-making. From reshaping pork nutrition and advocating for the return of well-marbled, flavorful pork to confronting the ongoing battle with PRRS and other health threats, Rob’s insights reflect decades of hands-on experience and bold innovation.

Key themes include: Nutrition Reimagined: Why the industry went off course—and how Brenneman Pork is leading change by prioritizing gut health, fat quality, and real performance.

Health & Survivability: Rob’s take on biosecurity, disease management, and the systems and protocols that protect both pigs and profitability.

Well-Marbled Pork as Premium Protein: The science, consumer insights, and culinary feedback behind Rob’s mission to reintroduce pork as a premium, flavorful protein.

Sustainability & Farm Culture: How Brenneman Pork balances environmental responsibility with day-to-day positivity and resilience.

Generational Impact: Strategies to attract, inspire, and retain the next wave of pork producers with pride and purpose.

Plus, a fast-paced finale where Rob shares his top pork pick, leadership lessons, and what he’d change overnight in the industry.

Whether you're a producer, nutritionist, policymaker, or future leader, this episode offers a masterclass in where pork production is headed—and how visionaries like Rob are shaping it.