Sorghum Tips

Nitrates & Prussic Acid in Forages, E-543 (2012)

Statewide

Applications in Sorghum Forages

When nitrates and prussic acid accumulate in forage, the feed may not be safe for livestock consumption. This Extension document—available for view, print, or download at https://agrilifebookstore.org/ (then use the search box) —highlights the symptoms of nitrate and prussic acid poisoning.

Prussic acid (cyanide) occurs primarily when a strong frost hits sorghum family forages or grain sorghum.  It can also occur in fresh growth on drought-stressed forages.  Cattle normally need to be off the forage at least 1 week after a frost or freeze, and properly cured hay should be OK.  Testing for prussic acid is tricky because handling the forage can lead to decomposition of the prussic acid.  If you need a prussic acid test decide first which lab you are going to use and call them ahead of collection for their instructions.

Nitrate accumulation in sorghum and sorghum hays is most likely in rainfed conditions when either significant N applications have been made or the crop is drought stressed but still accumulating N.  Nitrate is likely accumulated in the base of the stalk, so simple measures to use this forage include raising the cutting height 3-4”.  Drought stressed grain sorghum in the High Plains that may be used for hay should consider testing the forage for nitrate accumulation in 2012.

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