Quick Test for TMR Dry Matter

Dan Severson

University of Delaware Extension


A total mixed ration (TMR) is defined as a method of feeding cows that combines feeds formulated to a specific nutrient content into a single feed mix which contains forages, grains, protein sources, minerals vitamins and feed additives. This method of feeding has been highly adopted since the 1950’s because it allows cows to consume a nutritionally balanced meal with every bite. Feeding a TMR has both advantages and disadvantages.


The main advantage of feeding a TMR is improved feed efficiency. Each mouthful contains a balanced ration that leads to higher milk production and less metabolic upsets. In addition, the ability to use a variety of products to meet the nutritional demands of the cow allows flexibility in food sources, allowing for savings in ration building. The purchase of commodities in bulk is also often less expensive, adding further savings. Furthermore, the use of less favorable feeds can be masked by mixing all the ingredients with no reduction in feed consumption. TMR also lends itself well to mechanization.


However, the cost of equipment to implement a TMR can be a major disadvantage. Also, all cows in the group get the same ration. Individual feeding is not possible, so cows in a group should be of similar milk production, stage of lactation and body condition. Moreover, a TMR may not be economical for all herds by reason of facility design or use of pasture.


Dairy rations are formulated on a dry matter (DM) basis and the amount of each feed fed is on an as is or as fed (AF) basis. Feeding feed ingredients according to weight is only accurate if the moisture content of the feed is accounted for. Small changes in DM will change the nutrient profile of the ration. For example, a ration that is formulated to provide 25 pounds of DM per cow with corn silage at 35 percent DM. However, the actual corn silage content is 32 percent DM. This would leave the cow short on feed, resulting in a reduction in milk production and potential health problems.


As luck would have it, the DM content of feeds can be measured on the farm. The most commonly used methods of measuring DM are the Koster moisture tester or a microwave oven. However, a new quick test using a kitchen air fryer was recently demonstrated at the 2018 World Dairy Expo. This is a preferred alternative as it does not have to be watched because there is no way to accidentally start a fire. This new method also traps the fines inside the fryer enabling a more accurate DM analysis. The specifics for determining the DM of your TMR are as follows:


  • Weigh 100 grams of representative sample
  • Place the sample in the Air Fryer
  • Set the fryer to 250⁰F
  • Set a timer for 30 minutes
  • Record the weight of the dry sample
  • Calculate the DM content


To find the DM you will need to do some math – don’t worry, it is simple math. To figure out the DM content you will use the following equation:


Final Dry Weight (grams) / Initial Wet Weight (grams) X 100 = %DM


Here are the steps in determining DM of a TMR sample:


Set up your scale – set it to grams and tare to zero. Then weigh out 100 grams.





Place the sample in the air fryer basket.  Turn on your air fryer: set the temperature to 250⁰F and the timer to 30 minutes.




Record your final weight.  For this example, it was 45 grams. Now do the math to figure out the DM content.




Do you remember the equation?


Final Dry Weight (grams) / Initial Wet Weight (grams) X100 = %DM


The final dry weight for this sample is 45 grams.  Divide the 45 grams by the initial weight of 100 grams and multiply by 100 and you get 45% DM.


It is important to measure the DM content to maintain a more consistent diet and meet the needs of the animals.  The determination of DM should be used to adjust rations on a routine basis. The air fryer method is an easy way to perform DM analysis on the farm. The air fryer that was used for the DM testing was bought for less than $100 at a local box store. If your scale does not have grams, you can use ounces. There are roughly 28.35 grams in an ounce – 3.5 ounces equals 100 grams. The math equation will still be the same just change the grams to ounces. We currently have an air fryer located in the New Castle County Extension office, if you would like to try this method or you can use the Koster moisture tester located in Kent County Extension office. Feel free to contact me if interested or with any questions.


References available upon request.

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