Tips for testing hay

By Amber Friedrichsen, Associate Editor

Hay test results are like the nutrition facts labels of the forage world. They provide information about fiber and protein content, available energy, and overall forage quality.

Testing hay is especially important as producers make winter feeding plans. Analysis results can help guide decisions about how to feed the hay they have or how many bales they need to buy. In a recent article from Ohio State University Extension, Christine Gelley points out a hay test costs less than single round bale, and the results will likely pay for themselves.

Gelley, an agriculture and natural resources educator, outlines the steps to take to gather a representative hay sample and send it to a lab for analysis. Producers will need a hay probe or a pair of scissors to collect forage in addition to a bucket or similar container.

If using a hay probe, drill into the center of a bale from the wrapped side and empty the contents into the bucket. If using scissors, reach into a bale to get a sample, then cut hay into 4- to 6-inch pieces before putting them into the bucket. Repeat these steps until forage from 10 bales of the same lot has been collected. A lot is defined as hay from the same field and the same cutting.

Mix the 10 hay samples together to create one composite sample and transfer forage into a quart-sized plastic bag. Press and seal the bag and label it with your name and sample identification. Complete the sample information forms provided by your forage lab and submit these along with the hay sample.

Once producers receive analysis results, they can make more informed decisions about feeding and buying hay. With that said, Gelley notes understanding the key terms in test results is necessary to interpret forage quality. In addition to dry matter (DM) and crude protein (CP), she provides definitions for the following terms.

Adjusted crude protein (ACP): This is the value of CP corrected for heat damage. Use this value in place of CP when creating feeding plans.

Neutral detergent fiber (NDF): This is the total amount of fiber in forage that make up the structural parts of plants, including cellulose, hemicellulose, lignin, and silica. Lower numbers of NDF are associated with better feed intake and indicate higher quality forage.

Acid detergent fiber (ADF): While ADF accounts for cellulose, lignin, and silica, it also includes insoluble CP and ash. These are ultimately the least digestible components of forage. Therefore, low ADF indicates more energy is available to livestock.

Total digestible nutrients (TDN): This value represents all of the digestible crude fiber, protein, fat, and nitrogen-free components in forage.

Relative forage quality (RFQ): The RFQ is a metric used to rank forage quality that is determined with an improved formula used to index grass species and takes fiber digestibility into consideration. To calculate RFQ, multiply TDN by dry matter intake (DMI) and divide the product by the constant 1.23.

Gelley adds relative feed value (RFV) is another number provided by hay analyses that is calculated by multiplying DMI by digestible dry matter (DDM) and dividing the product by the constant 1.29. This number, expressed as a percentage, is comparable to the feed value alfalfa in full bloom, which has a RFV of 100; however, it does not account for fiber digestibility and may be a less accurate measure of forage quality.