Prevent Prussic Acid

With mother nature and the weather not cooperating this year, forage and roughage has been a challenge to put up.  We have seen an ample amount of sorghum and Sudan grasses planted this year, which is a fantastic way to utilize areas that were tough to get into. Yet there are a few things to remember when working with crops, namely Prussic Acid.  

Prussic acid is formed when the leaf freezes and ruptures the cell membrane within the leaf and allows the internal membrane components to mix. Equivalent to Cyanide gas Prussic acid can be lethal to livestock within minutes.

Depending on the temperature you may have just partial leaf damage, whole leaf damage or whole plant damaged.  While we have officially reached cold enough temps to produce Prussic acid harvest of the crop is still a possibility either through grazing, chopping, or haying.

If you plan on grazing sorghums, please remove all livestock before the frost event happens!  Even though the plant might not show any signs of frost stress until a couple of days later, membrane components will mix, and the plant becomes toxic immediately.  Livestock should remain out for 10-14 days to give the plant enough time to dissipate the toxic material.  One very important thing to remember is: Once it frosts and you start your day count, if it freezes again, you must start your count over until it freezes hard enough to kill the entire plant.  Once the plant has had a killing freeze, please make sure there is no new growth at the bottom of the plant. These tillers will have the ability to produce Prussic acid. 

Chopping silage is still a viable option as well because of the time it normally takes to get the product from the field to a pile and fermented.  Chopping the crop into 1-inch pieces then packing in a pile and allowing it to ferment for 30 days will allow the Prussic acid to dissipate even faster.   

If you plan on putting sorghum up as dry hay, you shouldn’t have much to worry about.  By the time you get the crop cut and it dries out enough to be raked, baled, and stored in a row, the gasses will have time to dissipate before you will ever use it for feed. 

The important thing to remember is Prussic acid is in all Sorghums and becomes lethal to cattle immediately after a frost or freeze.  Wait 10-14 days before you graze it, and until you have a killing freeze start your count over after every freeze!  If you have any questions, please don’t hesitate to contact us.


McKenzie Chambers
Purina Animal Nutrition LLC
Livestock Production Specialist
MAChambers@landolakes.com