Good nutrition is the foundation for maintaining a healthy and productive dairy herd. A ration that provides a balanced blend of protein, carbohydrate and mineral feedstuffs delivers needed nourishment.

“If you don’t have a balanced ration, you may compromise animal health and may not maximize production,” said Lisa Holden, an associate professor of dairy science at Penn State University Extension.

The total mixed ration (TMR) feeding method is designed to ensure that each bite across the bunk is nutritionally uniform.

“Cows need to consume as close to their actual energy requirements as possible while maintaining the physical or roughage characteristics, which we now refer to as feed particle size,” said Jud Heinrichs, professor of dairy science at Penn State University.

A balanced diet and a specific particle size are required for proper rumen function. Maintaining a steady state in the digestive tract of the animal assures peak performance, according to Heinrichs.

TMRs are also applicable to dairies that graze the herd.

“Most would agree that during the grazing season farmers need to complement the cows’ grass, alfalfa (and) clover intake with other feedstuff,” said Dennis Buckmaster, an agricultural engineer at Purdue University. “This would be a mixed partial ration (MPR) that includes things like grazing grain but (also needs) corn, wheat midds, etc., and that should be a blended thing.”

Determining the quantities of forage, feedstuffs and minerals to make a TMR is one part of the equation. Dairy nutritionists and veterinarians can provide guidance for designing rations for cows at various stages of life and production.

Choosing a mixer to properly blend the materials is another part of the equation and is the focus of the article that follows.

Why invest in a mixer?

Once the proportions of feed materials have been determined, creating a mixture that evenly incorporates the ingredients and creates a ration that cows will eat is key. Mixers improve accuracy of ingredient loading to reduce the errors through manual mixing.

“The mixer creates a blend that provides a ration that is balanced with each bite across the entire bunk,” Buckmaster said.

Mixers convert raw ingredients into palatable bites to ensure the cows eat a balanced meal. They shred silage and haylage particles into appealing lengths and grind coarse or whole grains into tasty morsels.

“Cows generally sort against long particles due to their less palatable nature and sort for finer particles in the ration,” he said.

From a productivity standpoint, mixers optimize labor use at feeding time, assure adequate blending of the ration and maximize equipment costs. And when the cows receive consistent, uniform rations, production in the milking parlor is enhanced.

Types of mixers

With a wide variety of makes and models, each offers similar, but slightly different features. Generally, mixers can be divided into two categories, tumble action and augers. Tumble action mixers, which include reel, tumble, ribbon and chain and slat models, use relatively little power to raise and lower the feed to achieve the TMR. Auger mixers, which are divided into horizontal and vertical, use a more aggressive mixing action.

David W. Kammel, professor at the University of Wisconsin-Madison, authored an article for eXtension that provides a through description of each type of mixer.

According to Kammel, the tumble mixer is a large drum with spirals and or pans on the interior circumference of the drum to lift and tumble the ration. A central auger moves feed from end to end and to the discharge door. A large part of the drum opens like a door to allow loading with a skid-steer or loader bucket.

Kammel explained that the reel mixer combines a set of augers and a reel similar to a combine reel in a hopper. Feed is lifted and tumbled by the reel moving it to the rotating augers, which provide a mixing action, move feed from end to end and to the discharge door, Kammel said. Knife sections on the auger flights cut or tear long, dry hay into 3- to 4-inch pieces and incorporate it into the ration. An optional hay pan allows the hay to be metered into the mixer providing the ability to break up large portions of dry hay or baleage.

Chain and paddle mixers use a tub or box containing a chain and paddles or slat conveyor to tumble the feed ingredients within the tub end to end. An auger at the front of the mixer provides additional mixing and moves material to the discharge door.

Auger mixers come in varying configurations. These mixers are described as horizontal or vertical. Buckmaster explained that horizontal augers have one, two, three or four augers to churn the feed in a hopper. The rotation speeds diameters, and flighting on the augers influence how the feed moves and blends and also how it is discharged.

Vertical mixers consist of a large tub with a single auger or twin augers. A planetary gearbox generally provides the extreme speed reduction needed to drive the screw. Knife sections are attached to the flighting to cut material. Movable shear or restrictor plates on the tub wall provide a shear surface, increasing the ability to process and reduce the particle size of large packages of hay. These units can process rations with almost 100 percent dry hay.

“Vertical augers are great because you can put (a) whole large round bale in and it will chop it up and create a mix,” Buckmaster said. “But they don’t clean out well. So small batches such as 20 percent of capacity won’t be mixed well since material can sit on auger and it won’t create churning action.”

In Kammel’s article, he includes mixing carts as an option for small herds. These scaled-down versions can feed approximately 12 to 24 cows per batch. There are chain and paddle, tumble and reel mixer cart designs on the market. Sizes range from 40 to 80 c.f. They usually are powered by a small 8 to 18 HP gas engines.

“The various designs have pros and cons,” Buckmaster said. “No one solution is always best. Some mixers (are) good with liquid ingredients; others are not. Some are designed for larger or smaller loads.”

Some mixers only work when fully loaded and won’t properly mix a ration when less full. Other models are designed to operate with smaller or less full loads. “You don’t want a large mixer if you’re only preparing small mixes,” Holden said. “Conversely, you don’t want to overload one either.”

“Generally, people think of sizing for the largest batch they want to mix,” Buckmaster said. “It’s as important to consider the smallest batch you want to mix.”

Material flow inside the mixer is a big deal. Proper blending only happens when there are no dead spots, no recirculating or non-fixing feed. “Most mixers are designed with this in mind; some do not have sufficient material flow to adequately blend liquids,” he said.

Improper flow mostly occurs when the improper size is chosen, making it even more important to properly size the mixer for the farm and ration.

Load accuracy

To optimize performance of total mixed rations and the mixer, it is imperative to measure, mix, test and monitor rations regularly. That can only be achieved when there are known quantities added to the mixer at the start of the feeding cycle.

Mixers are designed with scales to weigh the materials added to the mixer. The weighing system is usually supported at three or four places (points) on the mixer chassis depending on the design of the weight sensors.

Periodically, check the load cells to make sure the scales are accurate. “Put a known amount in the mixer to make sure it is accurate,” Holden said. “The manufacturer can provide recommendations for calibrating one.”

As technology has improved and electronic monitoring systems have become more advanced, electronics can provide data to a computer or mobile device for tracking purposes.

“TMRs are a little bit more efficient when linked with software that will record and track data,” Buckmaster said. “With data, a manager can know how long the mixer was running and whether or not the proper amounts were added to the mixer.”

For example, without scales and software, it’s nearly impossible to be confident regarding what went into the mixer. The goal may be 2,000 pounds, but on one day it could be 1,500 pounds, the next 2,200.

“If there aren’t records, you can’t track that and then you don’t have the opportunity to talk with an employee about being more careful with loading the mixer,” Buckmaster said.

Equipment improves consistency of particle size and blending, but still relies on a human operator. Make sure that the farm “feeder” has the necessary training to properly load the machine. “There is a proper order for loading the ingredients and the feeder has to know that,” Holden said.

Even with technology and training, errors still occur. The TMR that is designed on paper will not necessarily be what is delivered to the bunk. Load errors, human errors and what the feeder is doing contribute to discrepancies. The acceptable error threshold will vary from one farm to the next.

“The feeder should know the farm’s expectations for mixing errors.” Holden said.


Like any piece of equipment, mixers need maintenance. Moving parts need lubrication and knives need sharpening. It’s always best to consult the operator’s manual for guidelines specific to the machine. Buckmaster and Holden provide insight into the components that need regular attention.

“The knives chop coarse materials and need to be sharp,” Holden said. “Manufacturers provide instructions for the number of hours or loads the knives can handle before needing maintenance.”

It’s as important to check and maintain proper clearances between cutting elements as it is to sharpen the knives.

The mixer will also need frequent cleaning to ensure old feedstuff is not trapped in the machine and tainting future ration batches. Buckmaster provided a routine checklist that can be used regardless of mixer model or manufacturer.

  • Keep proper belt tension.
  • Keep proper chain tension.
  • Grease appropriately.
  • Check oil levels (always use the correct oil).
  • Operate PTO shaft at proper angle.
  • Use correct shear pins.
  • Maintain scales (protect wires; calibrate).
  • Keep proper tire pressure.


The mixer options available provide farmers with countless options. Before rushing to purchase a mixer, take time to consider which model is best suited to your farm. Budget often drives buying decisions, but it’s also important to think about mixer size, the type of feed in your TMR and whether a local service technician can provide assistance if a breakdown occurs.