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Agricultural Testing Services: Forage Sampling

Testing forage, grain or feed helps evaluate nutrient composition, determine potential animal performance and determine potential value. Testing enables matching of each feedstuff to the stage of production and class of animal, therefore supplying feed or forage in the most efficient manner.

How to Collect Samples

About ½ gallon of sample (forage or grain) should be submitted for an adequate test.

  • Hay – Obtain samples from about 10 percent of the bales in each lot of hay. The most accurate samples are obtained with the use of a forage sampling probe. For square bales, take one core from one end of each bale sampled. For round bales, take a sample from each side of the bale. If grab samples are taken, be sure to obtain a representative sample. A list of hay probe distributors is provided in our Forage Probe Listing.
  • Silage or haylage – If haylage is in round bales, follow the same procedures as those for round-baled hay. If haylage or silage is chopped, then obtain 2 to 3 gallons of material from 10 to 15 locations within the silo. For upright silos, run the unloader and collect one sample per minute for several minutes. In both situations, mix all the collected material together, then fill an airtight sample bag with this mixture. Be sure to seal bag to ensure correct moisture determination.
  • Grain or farm-mixed feed – Obtain several small samples from different areas of the bin or storage area. Combine into one composite sample. Noble's contract lab does not analyze commercially prepared feeds.
  • Fresh clippings – In a haying situation, standing forage should be cut at a height equal to the height setting on the swather from several areas throughout the pasture unit for a good representative sample. In a grazing situation, take a "hand-plucked" sample by trying to select parts of the plants the grazing animal is or will be consuming. Package all fresh samples in a sealed plastic bag to ensure correct moisture determination.

For additional information on collecting forage samples, view the How to Sample Forage for Haying or Grazing video.

Submitting a Sample

Fill out the sample information sheet. Identify the sample so that it's clear which forage it represents. Indicate what plant (bermudagrass, native grasses, alfalfa, etc.) and type (hay, standing forage, silage) of forage it is. This information allows for a more precise analysis and more accurate supplementation recommendations.

Recommended Forage Tests

To evaluate protein and energy (TDN), select test E. If you have alfalfa hay and want to know relative feed value (RFV), select test F. There is no charge for tests E and F, and results are mailed within two work days.

Tests E through K allow you to indicate the type of animal consuming the forage. The list of animals is on the back of the sample information sheet. Locate the animals you would like to use and enter the corresponding code number into the sample information. Noble Research Institute specialists will calculate supplemental feeding recommendations (if necessary) for that situation.

Receiving Results

After the information sheet is completed and turned in with the sample, the sample will be processed and sent to the appropriate laboratory for analysis. All requests for testing other than E or F will receive results in seven to 10 work days along with an invoice from the contract laboratory.

Sample Results

Explanation of Terms Used in Results

  • Dry Matter (%) – The percentage of the weight of your forage sample that is not water. Supplement requirements are calculated based on the dry matter percentage of your hay.
  • Moisture (%) – The percentage of moisture in the hay sample when it was tested.
  • Crude Protein (CP) (%) – The percentage of the hay that can supply nitrogen or amino acids to meet an animal's crude protein requirements.
  • Acid Detergent Fiber (ADF) (%) – The percentage of the hay that is considered to be very slowly digested. It contains cellulose and lignin.
  • Neutral Detergent Fiber (NDF) (%) – The entire fibrous portion of the hay. NDF contains ADF plus some more rapidly digested carbohydrates.
  • Total Digestible Nutrients (TDN) (%) – A calculated value (estimated from ADF) that represents the overall digestibility or energy value of the forage.
  • Relative Feed Value (RFV) – A calculated value that represents the digestibility and intake potential of the forage. It is calculated from ADF and NDF and is only nutritionally applicable to alfalfa hay fed free choice to dairy cows. RFV is often used in marketing all types of hay.
  • Dry Matter Intake (DMI) – An estimate of the amount of forage the animal will voluntarily consume if given free access. It is expressed in pounds per day and is estimated from TDN of the forage. Actual DMI may vary considerably due to environmental and other effects.
  • Nitrate Nitrogen (NO3-N) The following table can be used to interpret nitrate nitrogen results.
NO3-N, ppmRecommendation
0 - 750 Considered safe for all cattle.
751 - 1,150 Considered safe for non-pregnant cattle
1,151 - 2,250 Some risk for all cattle. May cause abortion and decreased growth.
>2,250 Potentially toxic for all cattle. Acute toxicity symptoms, including death.

OSU Extension Facts F-2903, "Nitrate Toxicity in Livestock," Oklahoma State University, provides more information and suggestions for feeding forage high in nitrate.

Using the Results

Results are reported on an as-fed basis on the top line of the results section. These numbers are useful when weighing out forage or supplements to feed cattle. The bottom line of the results section is the analysis on a dry-matter basis. These values represent the forage with the water removed. Dry matter values should be used to calculate supplement needs, to compare one forage to another, or when buying and selling hay.

For a cow-calf producer, two important values are CP and TDN. Beef cow nutrition is commonly discussed in these basic terms.

If you selected tests E through K (which include ADF), our database has calculated CP and TDN deficiencies, and if any deficiencies exist, recommended supplements for the animals you selected. Default animals will appear if specific animal codes were not indicated when the sample was submitted. Default animals are:

  • 1,200 lb mature cow, early lacation, average milk production
  • 1,200 lb mature cow, middle gestation
  • 800 lb yearling bred heifer, late gestation, ADG of 1.0 lb

If there is a deficiency, find the supplement in the list with the lowest cost. This is typically the most economical supplement to use. Prices are updated about every two months and are an average of feeds available in the Noble Research Institute's service area. Check with your feed supplier to confirm supplement prices.

When using supplement recommendations, be aware of the following:

  • Actual dry matter intake and nutrient requirements may vary considerably from estimates due to environmental conditions and inherent animal variation.
  • You should almost always supplement to meet a CP deficiency, or dry matter intake will be less than expected.
  • You should supplement to meet a TDN deficiency when animals need to gain or maintain weight or condition.
  • Always provide a quality mineral supplement and adequate clean water.
  • Closely monitor cattle performance and body condition to be sure nutrient requirements are being met.

If you have any questions concerning your forage analysis, call a Noble Research Institute livestock specialist using the Ag Helpline at 580-224-6500.

Mailing Information

  1. Write the sample name and crop ID on bag. This is important for identification during the laboratory process, especially when more than one sample is submitted. Testing takes about seven to 10 working days from the time we receive your shipment.
  2. Be sure the name, address and sample ID on the Forage Sample Information Sheet corresponds to information on the bag.
  3. Do not send cash or check. Forage testing types E and F are free to Noble cooperators. Please refer to Test Analysis Pricing for test type information and Servi-Tech Lab costs. Noble does not charge for its services. When you receive your test results, you will receive an invoice from our contract laboratory for testing analysis.