UNL BeefWatch · University of Nebraska-Lincoln

Managing Annual Forages After Frost

October 7, 2025·11 min·1 clip

Aaron Berger and Ben Beckman discuss managing annual forages after frost in an unusual year with 90-degree October temperatures.

This episode of the UNL BeefWatch podcast focuses on managing annual forage crops after frost events to prevent livestock poisoning. Host Aaron Berger, a Nebraska Extension educator, interviews Ben Beckman, the author of a related newsletter article and an extension educator based in San Diego. They discuss the specific risks frost poses to certain forage types and the necessary management adjustments. The conversation centers on the dangers of prussic acid poisoning in sorghum, sudangrass, and sorghum-sudangrass hybrids following a frost. Beckman explains that these forages can accumulate cyanogenic glycosides, which convert to prussic acid when plant cells are damaged by freezing temperatures. He stresses that the risk is highest in new growth and young, leafy plants after a frost event. The hosts note that while recording in early October, conditions were unusually warm, nearing 90 degrees, delaying typical frost concerns. They advise producers to monitor local weather forecasts closely for impending frosts. Beckman recommends removing cattle from at-risk forages before a frost occurs as a primary safety measure. He suggests waiting for a killing freeze and for the forage to dry down completely before regrazing. A key insight is that the danger period can last for several days to a week after a frost, as the plant tissue dries and releases the toxin. Beckman clarifies that properly ensiled or hayed forages from these species pose no risk, as the curing process dissipates the prussic acid. He contrasts this with nitrate poisoning, a separate issue linked to drought stress rather than frost. The hosts emphasize that johnsongrass, a common weed, also carries a prussic acid risk after frost. Beckman advises producers to test forages if there is any uncertainty about prussic acid or nitrate levels before grazing. The tone is educational and conversational, with two extension experts providing practical, science-based recommendations. The style is direct and advisory, aimed at delivering timely, actionable information to cattle producers. This episode is essential for livestock producers grazing annual summer forages in regions prone to autumn frosts. Listeners seeking broad ranch management topics or those in frost-free climates may find the content too specific.

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