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OSU Extension

College of Food, Agricultural, and Environmental Sciences

November 3, 2023 - 8:29am --

We were joking with our son the other night that he has been replaced as my wife’s favorite child by the dog.  However, it appears that Zues is trying to work his way down the list.  He began by digging up Jessica’s flower beds.  She successfully worked to break him of that habit.  Now instead of digging up the flower bed he is just digging random holes in the yard.  Jessica just smiles and tells me it is my problem now.

This week I would like to continue our discussion of forage testing, with a brief explanation of forage testing results.  Up to this point we have talked about why to sample, and how to sample.  Now we need to put it all to use.  You may not be a nutritionist, but you need to have a basic understanding of what your sample results are telling you.  This is important because it is vital information to ensure you are meeting the needs of your livestock, but it will also be important to help guide your forage management decisions in the future.  It can also be valuable information if you are selling the forages, as forages with higher nutrient content are obviously worth more than lower quality products.

The first number you will often look at is percent Dry Matter (DM).  Percent dry matter is simply a measure of how much of your forage is plant material and how much is water.  This number is important as most of the nutrient values on the remainder of the report are provided based on dry matter content.  Dry matter content will also give you an idea of how well the forage will store and how quality of the forage will be maintained until used.  Dry round bales should be around 82% DM or higher, and square bales 80% or higher to elevate concerns of overheating and potential barn fires.  Forages that are wrapped or ensiles will be stored at lower DM that ranges from 70% down to 25% depending on if it is wrapped bales for chopped product stored in a silo, bag, or bunker.  For wet forages, if DM is too high you can get heating issues that reduce quality or poor fermentation.  If DM is too low for the storage method you can improper fermentation, decreased shelf-life, and excessive seepage and nutrient loss.

As mentioned, the nutrient values on the remainder of the analysis are reported as a percent of dry matter.  Crude Protein (CP) is the amount of nitrogen in the feedstuff.  It will typically fall in a range of 4 to 20 percent.  If we want to express this in pounds, let consider the following example.  You have 100 lbs of hay that is 90% dry matter.  This sample contained 90 lbs of plant material and 10 lbs of water.  If the sample results said you have 10% CP, then 10 percent of the 90 lbs is 9 lbs of CP meaning that for every 100 lbs of the hay you are feeding, your animals are getting 9 lbs of CP.

Acid Detergent Fiber (ADF) and Neutral Detergent Fiber (NDF) represent the fiber content of the forage.  ADF is the amount of cellulose and lignin in the plant.  It estimates how much of the forage is indigestible to the animal.  Most forages average 40% ADF.  NDF is a value of all the plant cell wall material and is the primary determinant of potential consumption by the animal.  Unlike ADF, NDF has no bearing on the quality or digestibility of the forage and will range from 50 to 80%.

Ash percentage is a measurement of potential total mineral content and important for the calculation of Total Digestible Nutrients (TDN).  While the amount of minerals will be wrapped up in the percent ash reported, they are not all that is included.  Knowing the percent ash can also tell you a little about how you harvested the forage, especially hay.  If the ash value is too high it could be a sign that you may have had the rake set a little too low and picked up a lot of extra dirt when you were baling.  The specific mineral concentrations are not typically reported on a standard forage sample result.  These are typically specialized tests that you will need to request and pay extra for.  It is a good idea to have these tests run periodically so you understand what minerals may be deficient to target in a supplementation program.

Finally, TDN is an estimation of the energy content of the forage and is calculated using the values from your ADF, NDF, CP, and ash results.  As the TDN value increases, the percentage of the forage that will be utilized by the animal increases.  Most low quality hays can range 40 to 50% TDN, high quality grass forages will be 50 to 60 % TDN and most legume based forages will be 60 to 70% TDN.  Next time we will wrap up with a discussion of matching forage quality with animal needs.

We are working on our winter program line up for 2024.  So, we will be able to announce our annual pesticide recertification offering.  I also want you to be watching for the schedule for our Professional Marketer series.  We will hold an advance commodity marketing school during the month of February.  The program will feature the top University and private industry experts on grain, livestock, and milk marketing.  We plan to have the topic line up out by the first of December.  As always, If you have questions your forages, or any other livestock or farm business questions, please feel free to contact me at the OSU Wayne County Extension office at 330-264-8722, or email me at  Even better is to stop by our office for a chat.  I look forward to meeting everyone and I hope you have a safe harvest season.

John Yost is an Extension Educator IV, Agriculture and Natural Resources, at OSU Extension-Wayne County.
This article was previously published in The Daily Record.