Beware of Prussic Acid Poisoning as Frost Approaches

Although prussic acid poisoning can occur anytime during the growing season, the greatest risk is usually associated with the first frost in Kentucky.

The primary cause of hydrocyanic (prussic) acid poisoning in domestic animals is the ingestion of plants containing this potent toxin. Cyanide-producing compounds (cyanogenic glucosides) occurring in living plant cells are converted to prussic acid when cells are crushed or otherwise ruptured.

The prussic acid potential of plants is affected by species and variety, weather, soil fertility and stage of plant growth. Plants of the sorghum group and leaves of wild cherry trees have a potential for producing toxic levels of prussic acid. There are wide differences among varieties. Some of the sudangrasses are low in prussic acid. Pearl millet is apparently free of prussic acid in toxic amounts.

According to UK Extension Specialist Dr. Garry Lacefield, the risk from potentially dangerous forages may be reduced by following certain management practices:

1. Graze sorghum or sorghum cross plants only when they are at least 15 inches tall.

2. Do not graze plants during and shortly after drought periods when growth is severely reduced.

3. Do not graze wilted plants or plants with young tillers.

4. Do not graze for two weeks after a non-killing frost.

5. Do not graze after a killing frost until plant material is dry (the toxin is usually dissipated within 48 hours).

6. Do not graze at night when frost is likely.

7. Delay feeding silage 6 to 8 weeks following ensiling.

8. Do not allow access to wild cherry leaves whether they are wilted or not. After storms always check pastures for fallen limbs.

For more information on Prussic Acid Poisoning, along with other Forage-Related Disorders,  contact the McLean County Extension Office  at (270)273-3690.   Educational programs of the Cooperative Extension Service serve all people regardless of race, color, sex, religion, disability or national origin.