Testing for Prussic Acid Content in Forages

Mark Sulc, Extension Forage Specialist, The Ohio State University

An accompanying article describes the species that can develop prussic acid poisoning potential and management practices to follow to prevent poisoning of livestock with those species after a frost. If doubt remains regarding the safety of the forage, the forage can be tested for prussic acid (HCN) content. But keep in mind that prussic acid is a gas, so it is difficult to detect in samples sent to labs. Sample handling is extremely critical to ensure that the lab test will be representative of what is being fed to livestock.

Obtain a representative FRESH sample of the forage to be fed. Collect 1 to 2 lbs of fresh forage from across the field to be grazed. For silage, follow proper sampling protocol to obtain a representative sample.

Do not allow the sample to dry. Place in an air-tight plastic bag, freeze the sample quickly, and ship the fastest way (overnight express) in a cooler with an ice pack.

Remember, HCN content dissipates with drying of the sample. So if the sample arrives at the lab drier than the fresh forage that is fed, a false negative result will likely occur.

The following are two labs that will analyze samples for prussic acid (cyanide). Other labs may provide testing for prussic acid, always call ahead to confirm whether the prussic acid test is provided and to ask about sample handling protocols.

The Michigan State University Animal Health laboratory
Diagnostic Center for Population and Animal Health
Michigan State University
4125 Beaumont Road
Lansing, MI 48910-8104
TEL (517) 353-1683, FAX (517) 353-5096
Request Procedure 70022

Cumberland Valley Analytical Services, Inc.
14515 Industry DriveHagerstown, MD 21742
TEL: 1-800-282-7522, FAX (301) 790-1981