How a TMR wagon mixes a dairy ration

A total mixed ration wagon weighs forages, grains, protein and minerals into a tub where spinning augers tumble and cut them into one uniform mix, so every bite a cow takes has the same nutrients. Rations are balanced on a dry matter basis, so the wagon operator must account for how much water each wet ingredient carries.

Controls

Labels

Animation speed

Corn silage (as fed)

Haylage (as fed)

Grain mix fills whatever is left of the batch.

Cows to feed

Step through it

Weigh inLoad cells under the tub weigh each ingredient as it is loaded, following a recipe for that pen of cows.
Vertical augersTapered screw augers lift feed up the center and let it fall down the sides, folding the batch over and over. Knives on the flights cut long forage.
Wet versus dryCorn silage is often about two thirds water, while grain is nearly dry. Swapping silage for grain raises the ration's dry matter sharply.
Do not overmixA few minutes after the last ingredient is enough. Overmixing chops fiber too short, which can upset the rumen.
DeliverThe discharge door opens and a conveyor lays the ration along the feed bunk in front of the cows.

Dry matter from the recipe

Ration dry matter is a weighted average: multiply each ingredient's share of the as fed batch by its own dry matter, add them up, and divide by the total. The model assumes corn silage at 35 percent dry matter, haylage at 45 percent and a grain mix at 88 percent, typical values that real farms check by testing.

Batch weight then follows from how much dry matter the cows should eat: as fed weight = cows x dry matter per cow / ration dry matter fraction. The model uses 25 kg of dry matter per cow per day as a round teaching number.

Try it: start at 50 percent silage and 20 percent haylage, then drop silage to 30 percent. Ration dry matter rises from about 53 to about 63 percent and the batch needed for 100 cows falls by several hundred kilograms, even though the cows get the same dry feed.

Why testing matters

Silage dry matter drifts with weather and with where in the pile it is taken. If silage gets wetter and nobody adjusts the recipe, cows quietly get less dry feed than planned, so many farms test forage moisture weekly.

Sources

Feeding total mixed rationsUniversity of Minnesota Extension
Total Mixed Rations for Dairy CowsPenn State Extension
Stabilizing Total Mixed Ration Dry Matter to Mitigate Environmental-Relative-Humidity Effects on Lactating Cow PerformanceAnimals, MDPI (open access)

How to cite this model

Avid Solutions International. (2026, November 11). How a TMR wagon mixes a dairy ration [Interactive 3D model]. Avid Field Lab. https://avidsolutionsintl.com/explore/tmr-feed-mixer

Last updated November 11, 2026

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