Grain and Silage Sampling and Mycotoxin Testing
If corn ear rots were a problem in the field, it is important to test harvested grain for mycotoxins. Obtaining a representative sample for mycotoxin testing is critical for accurate results. It’s also important to know that testing methods vary in accuracy.
The accuracy of a mycotoxin test result largely depends on the quality of the grain or silage sample. The United States Department of Agriculture (USDA) Grain Inspection Handbook and the Canadian Grain Commission recommend specific sampling methods to ensure that samples accurately represent the grain population and silage mass. Sample collection methods vary depending on whether the sample is collected from the field (combine), a grain truck, a shipping container, feed bunks or storage bins, or at the elevator or point of sale.
What does a representative sample consist of?
Although sampling methods vary, the size of the representative sample is consistent. According to the USDA Grain Inspection Handbook, a representative sample is at least 4.4 pounds, and preferably 5 pounds (2-2.5 kg). In many cases, several subsamples will be taken and then combined into a single composite sample (Figure 1).
It is recommended that each subsample for the composite sample be at least 4.4 pounds (2 kg). Combine these subsamples to make a single composite sample. Mix the composite sample thoroughly, and then take a final 5-pound (2.5 kg) sample from the composite for further testing. When sampling grain, gather the subsamples several different times from a moving stream of grain while the grain is being loaded or unloaded. However, sample probes are commonly used for stationary loads of grain. Silage subsamples should be removed from both vertical and horizontal facing areas of the silage mass.
Figure 1. Several subsamples of corn are pooled to form a larger representative sample.
Don’t Rely on Appearance Alone
There are several technologies for testing mycotoxin concentrations in corn grain and silage. Never rely solely on visual methods such as the black light test (Figure 2). Visual test results can be inconsistent, so always test samples using recommended methods, or send them to professional laboratories.
Figure 2. Fluorescence under a black light is not a useful way to determine if grain is contaminated with a mycotoxin.
Several companies sell kits that detect and measure specific mycotoxins. Using such kits will require an initial investment of several thousand dollars to purchase the proper testing equipment. However, once you have the equipment, the cost of testing a single grain sample (a subsample of a larger sample) for one particular mycotoxin is usually less than $10 (Figure 3).
Companies that sell mycotoxin detection equipment and test kits include:
Figure 3. A corn sample being tested for mycotoxins using supplies from a test kit.
Local laboratories and grain inspection services may test individual corn samples for mycotoxins. Below is an incomplete list of select grain testing providers. Check with your local Extension office for a more complete list of grain testing facilities in your area. For a list of labs in Ontario, visit here. Costs and sample submission procedures vary by provider.
Barrow-Agee Laboratories (Memphis, Tennessee)
Breathitt Veterinary Center (Hopkinsville, Kentucky)
Cumberland Valley Analytical Services (Hagerstown, Maryland; Batavia, New York; Zumbrota, Minnesota)
Dairy One (Ithaca, New York)
Dairyland Laboratories (Arcadia, Wisconsin)
EMSL Analytical, Inc. (Baton Rouge, Louisiana, plus locations in Florida, Georgia, North Carolina, and Texas)
Eurofins Central Analytical Laboratory (Forsyth, Georgia; New Orleans, Louisiana)
Fort Worth Grain Exchange (Fort Worth, Texas) 817-626-8213
Holmes Laboratory, Inc. (Millersburg, Ohio)
Indiana Animal Disease Diagnostic Laboratory (ADDL) at Purdue University (West Lafayette, Indiana)
Indiana Crop Improvement Association (Lafayette, Indiana)
Kansas Grain Inspection Service (Topeka, Kansas)
Midwest Laboratories (Omaha, Nebraska)
Midsouth Grain Inspection Services (Memphis, Tennesee; Stoneville, Mississippi; Little Rock, Arkansas)
Minnesota Valley Testing Laboratories, Inc. (New Ulm, Minnesota)
Quanta Lab (Selma, Texas)
Romer Labs (Union, Missouri)
Trilogy Analytical Laboratory, Inc. (Washington, Missouri)
University of Kentucky Veterinary Diagnostic Lab (Lexington, Kentucky)
Waters Agricultural Laboratories, Inc. (Owensboro, Kentucky)
Waypoint Analytical (Leola, Pennsylvania) email@example.com)
Charles Woloshuk, Purdue University; Tom Allen, Mississippi State University; Martin Chilvers, Michigan State University; Travis Faske, University of Arkansas; Anna Freije, Purdue University; Tom Isakeit, Texas A&M University; Daren Mueller, Iowa State University; Trey Price, Louisiana State University AgCenter; Damon Smith, University of Wisconsin; Albert Tenuta, OMAFRA; and Kiersten Wise, University of Kentucky
Gary Bergstrom, Cornell University; Carl Bradley, University of Kentucky; Alyssa Collins, Pennsylvania State University; Andrew Friskop, North Dakota State University; Doug Jardine, Kansas State University; Hillary Mehl, Virginia Tech University; Alison Robertson, Iowa State University and Adam Sisson, Iowa State University
All photos were provided by and are the property of the authors and contributors except Figure 2 by John Obermeyer, Purdue University.
Funding for this project was provided by the United States Department of Agriculture - National Institute of Food and Agriculture (USDA-NIFA) project Integrated Management Strategies for Aspergillus and Fusarium Ear Rots of Corn. NIFA Award Number: 2013-68004-20359. We also thank the Grain Farmers of Ontario for support.
This publication was developed by the Crop Protection Network. The Crop Protection Network is a multi-state and international collaboration of university/provincial extension specialists and public/private professionals that provides unbiased, research-based information to farmers and agricultural personnel.
This information in this publication is only a guide, and the authors assume no liability for practices implemented based on this information. Reference to products in this publication is not intended to be an endorsement to the exclusion of others that may be similar. Individuals using such products assume responsibility for their use in accordance with current directions of the manufacturer. May 2020
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