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Mixing a good TMR – What can go wrong and what to look for

Jeff Weyers Published on 28 June 2013
feed mix

Troubleshooting a problem on a dairy is a multi-faceted endeavor.

Usually, no one specific area will tell the whole story, and most of the time the problem started weeks ago.



Since feed continues to consume roughly 70 percent of total gross revenue on the dairy and because it’s linked to many different issues that arise, it becomes the target of many troubleshooting schemes.

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Every aspect of day-to-day feed management should be closely monitored. This article will focus entirely on mixer wagon function and, most importantly, maintenance.

Mixer wagons are the heart of any total mixed ration (TMR). Mixing equipment (wagon, tractor, loader) can cost in excess of $250,000. This equipment is critical to the success of the dairy.

There are many different brands of wagons, and each has their own specific engineering details.


The area of feed management that receives the least attention but should require the most is constant analysis of the mixer wagon.

Things to look for:

  1. Look inside. I always recommend looking in the mixer wagon prior to the first load of the day.

    The feeder needs a basic understanding of what the components (knives, kicker plate) look like and how they function.

    He should be aware of how many knives there should be on each auger and what they look like when they need to be replaced.

    By checking often enough, the feeder can establish maintenance guidelines on the equipment.

  2. Look inside, again. Safely climb up the manufacturer’s ladder or platform to visually appraise the inside of the mixer box when mixing a TMR.

    The most obvious thing to look for is “dead spots,” meaning feed that is not moving.Specifically look at areas around the discharge doors.


    If the door area is worn out, it will create a depression for feed to get caught and will stop feed from being picked up by the kicker plates and augers. Watch the load from start to finish.

    The wagon will move feed around differently as more weight is added.

    Establish a visual of how your mixer is working when all the components are new. Also, mixer wagons work better at higher tractor RPMs.

    A common mistake is running the tractor RPMs too low; this will cause “dead spots.” If you see a dead spot, increase RPMs to see if this cures the issue.

  3. Monitor loading technique. The best way to see how the load is mixing is watching it from start to finish. Many times, feeders get in a hurry to load the mixer.

    When loading wet ingredients or ingredients with small inclusion rates, it’s best to load down the sidewall of the wagon instead of dumping the ingredient directly over the augers.

    Wet feed will stick to the augers, and if you follow a wet ingredient with a fine-meal feed, it will tend to stick to that wet auger.

    If this is a small load (i.e., pre-fresh diet), it will be a problem since the wagon will never get full enough to work feed over the entire auger.

  4. Monitor unloading technique. There are many different scenarios as to how well a TMR unloads from the wagon. What I recommend to the feeders is to find the most efficient method to unloading.

    This includes proper tractor RPM to keep the feed moving in the mixer. Feed is in constant motion from front to back, and tractor RPM is important for proper cleanout at the end of the load.

    Feeders need to monitor speed and proper discharge door control to provide a consistent flow of feed to the feedbunk. Amount of feed, feed distribution and timing of feeding is critical to managing the feedbunk.

The most popular question I get when visiting a dairy is: “What is the best mixer wagon?” This is not a simple answer. I’ve compiled a list of questions to aid management in making this decision.

When determining what mixer will work best for your dairy, use this simple checklist:

  1. Where is the closest dealer? If you don’t have a dealer close by for parts and repairs or for allowing you to demo the machine, I have a hard time recommending that mixer. A dealership that has a replacement mixer in case of a major breakdown is a huge asset.
  2. How much dry hay is in your ration? This will determine the need for a vertical mixer or a horizontal one. Horizontal wagons still do an excellent job of mixing feed when low-inclusion rates of dry hay are used.
  3. Is there a brand you are familiar and comfortable with? It’s human nature to wonder why your neighbor uses a specific brand. The more familiar you are with a brand, the quicker you will recognize problems and keep the equipment running more efficiently.
  4. How often do you service your equipment? Let’s be honest with this question. All mixer wagons work as intended when they are new. There is a tremendous amount of feed that goes through your mixer every day.

For example, a 1,000-cow dairy will run approximately six to eight loads of feed per day. Assuming a 15,000-pound batch size, 8 loads x 15,000 pounds = 120,000 pounds TMR daily. Therefore, in six months’ time, roughly 432 semi-truck loads of feed are going through the box.

The internal components will wear out and require periodic servicing or replacement. Bottom line: After six months, don’t expect the wagon to perform like the day it arrived to the dairy.

The mixer wagon is a very critical part of the dairy’s success. Training your feeder to understand the mixer wagon and how to recognize potential issues will help discover major problems in mixing and delivering feed before they happen.

Maintaining a tightly managed feed operation from the mixer wagon to the feedbunk will allow your nutritionist to troubleshoot more effectively and efficiently. PD

PHOTOS:Typical “dead spot” in front of mixer. Feed is not moving at all against front discharge door. Photos courtesy of Jeff Weyers.

Jeff Weyers is a Global Technical Specialist - Dairy with Vi-COR. Email Jeff Weyers.