Testing for Nitrates

Dr. Maurice Eastridge and Dr. Bill Weiss, Dairy Specialists, The Ohio State University

With the dry conditions in many areas in Ohio, crop growth has been severely affected and producers are considering using grain corn for forage. With the dry conditions, concerns have arisen about the potential for nitrate toxicity of animals. Conditions favorable to high nitrate concentration and feeding guidelines are described in the OSUE fact sheet titled "Nitrates in Dairy Rations" (http://ohioline.osu.edu/as-fact/0003.html).

Options for testing for nitrates are sending samples to feed analytical laboratories or using field test kits. Many analytical laboratories test for nitrates with a very fast turnaround time for results, but the samples must be properly handled (call the laboratory for instructions before the sample is sent). The following laboratories, among many others, offer nitrate analyses:

Holmes Laboratory, Millersburg, OH, (800) 344-1101
DairyOne, Ithaca, NY, (800) 344-2697
Cumberland Valley Analytical Services, Maugansville, MD, (800) 282-7522
Spectrum Lab, Washington C.H., OH, (800) 321-1562

Field test kits are available from different suppliers, but many of these are designed for water and must be modified for feed. Some suppliers of test kits are:

QA Supplies (http://www.qasupplies.com), (800) 472-7205
Nasco (http://www.enasco.com), (800) 558-9595
Nitrate Elimination Co., Inc. (http://www.nitrate.com), (888) 648-7283

To use the test kits designed for water to analyze for nitrates in corn plants, follow the procedure below:

  1. Chop a representative sample of corn plants into very small pieces and mix
  2. Weigh about 20 grams of the chopped corn silage and add 100 ml of distilled water
  3. Let the mix stand for about 10 minutes, shake vigorously, and repeat this step two or three times (a better approach would be to mix the silage and water in a blender)
  4. Remove 5 ml of the solution and add 95 ml of distilled water and mix
  5. Run the test using the kit that you have purchased.
  6. Convert the results to a dry matter basis, using one of the following methods:
    a. Test result x 400 = ppm (DM basis, assuming the corn is 30% DM)
    b. Analyze the DM content of the corn silage and use the following equation: (test result x 120) / DM proportion, expressed as a decimal = ppm

    *If values are below the detection limit of the assay, nitrate concentration in the plants should not be a problem for the animals.