Feed Mixers

Mixing your own rations for livestock can be tricky. Improperly mixed rations won’t provide the correct balance of energy, protein and nutrients for your animals. Selecting the right mixer maximizes nutrition, increases feed economy and simplifies custom blending.

Mixer basics

“Mixers should be matched to the type of ration fed,” said Dr. Karl Hoppe, area extension specialist for livestock systems at North Dakota State University’s Carrington Research Extension Center. “Vertical mixers work well for high-forage rations, ribbon mixers work well for general use, and horizontal mixers work well for high-grain rations.”

The purpose of any mixer is to consistently provide a homogenous mix. To optimize mixer function, you must select the right type of mixer for your rations and use it correctly.

According to “Design, Selection, and Use of TMR Mixers” (http://bit.ly/1oFKUNn), written by David Kammel, professor of agricultural building design at the University of Wisconsin-Madison, there are a handful of mixer designs: horizontal auger, reel, tumble, vertical, and chain and paddle.

Some mixers have knife sections, giving them the ability to cut long, dry hay into short pieces to add to the ration. According to Kammel, this feature was a result of consumer demand and was added to some mixer types less than a decade ago. Even in mixers designed to handle large hay rations, grass-based hays tend to cause problems, as the grass wraps around augers and is difficult to fully incorporate. Alfalfa-based hays are less problematic, since they readily shred.

“If whole large bales of hay or baled silage are used without preprocessing, vertical mixers are the only real option,” said Dennis Buckmaster, professor of agricultural and biological engineering at Purdue University. “This is their strong point. For rations with chopped silages and limited amounts of hay, reel and auger can do the best job in the least amount of time. Auger mixers cause a bit more size reduction than reel mixers. Reel mixers offer a good combination of mechanical and tumble action,” he explained.

For the study, Dr. Karl Hoppe and Al Ulmer sampled rations from three pans: one each at the beginning, middle and end of the bunk line. A nutritional analysis of the feed samples was also performed.

No matter the type of mixer, mixing compartments aren’t designed to be filled to capacity. Mixers are rated, depending on the manufacturer and model, for operating at 60 to 90 percent of the full capacity. The mixing capacity is not the same as the total volume of the mixing compartment.

“Filling the mixer to about 85 percent full does a much better job of mixing [than filling to capacity],” said Al Ulmer, LaMoure County agent for North Dakota State University Extension Service.

Buckmaster said, “Blending requires material flow. Mixers need space left in them for material to flow, so they cannot be filled to volumetric capacity – to the brim, level full – and still function correctly.”

Mixer carts are smaller versions of the standard mixer types. With a small herd of one or two dozen cows, mixer carts may be a more economical choice. Using too large a mixer can impact its accuracy.

Getting the right mix

It doesn’t work to dump all the ingredients into the mixer randomly and hope for the best. Correct ingredient order, proportions and timing are essential.

Mixers vary in material flow and aggressiveness of the mixing action. The wrong batch size can negatively impact flow, resulting in overmixed, unmixed or undermixed materials. Results are also affected by the amount of mix time and the order in which liquids and small or large-particle rations are added.

“The rations should be mixed for a period of time before [being] fed. Filling the wagon at the feed source and driving across the yard and dumping may not be enough time to thoroughly mix the ration,” Ulmer said. “How the feeds are added can influence how well it mixes the ration.”

Particle size reduction occurs as the mixer moves the ingredients. Sometimes this is desirable, but size reduction can impact the roughage value of the ration. Depending on the manufacturer, there are different recommended protocols for adding mix ingredients, and these should be followed. For example, some models require hay to be added first; others stipulate that grains be first.

Al Ulmer, LaMoure County agent for NDSU Extension Service, said, “The rations should be mixed for a period of time before [being] fed. Filling the wagon at the feed source and driving across the yard and dumping may not be enough time to thoroughly mix the ration.”

“Think revolutions, not minutes, when dealing with time,” Buckmaster said. “If one mixer operator mixes four minutes after the last pound of the last ingredient is added with the engine at 2,200 rpm, and another mixer operator mixes for five minutes, but with the engine at reduced throttle (1,600 rpm), then it is the first operator who runs the mixer 10 percent longer.”

If you’re adding medications or other supplemental, dosage-based ingredients to the feed mix, pay attention to proper timing and sequencing of ingredients. Adding small amounts of supplements to feed can be tricky, and doing it effectively depends on the other ingredients in the ration.

“Basically, small quantities of feeds need to be diluted with larger quantities of similar feeds, then mixed with other feeds,” Hoppe said. “Try to avoid adding small quantities to the mixer right after a large amount of wet feed is mixing, as this usually prevents adequate dispersion. Some situations might require another smaller mixer to dilute and adequately mix the supplement before adding to a larger mix.”

Drug carryover from one batch to the next is a concern. Medicated feed residuals can remain in the mixer due to electrostatic charges. Feed particles can also be stuck in the discharge augers or on the mixer bottom.

Monitoring the mixing

Optimizing feed efficiency requires knowing exactly what each animal is being fed. With feed costs rising, providing properly mixed rations has become even more critical. Animal performance should improve as mixed rations become uniform and geared to the animals’ needs. With this in mind, Ulmer and Hoppe conducted a study on mixer use in feedlots in North Dakota.

“You can use a marker, like candy, where you can count and visually assess the mixing as it is delivered into the feed bunk,” Hoppe explained.

For the study, candy was added to the feed mix while farmers mixed as usual. Mixing effectiveness was visually assessed by examining the dispersal of the candy. The researchers performed a nutritional analysis of feed samples and generated a coefficient of variation (CV) report and recommendations for improving mixer performance for each farm. Information about the study is available at http://slidesha.re/WLzAVQ.For the study, Dr. Karl Hoppe and Al Ulmer sampled rations from three pans: one each at the beginning, middle and end of the bunk line. A nutritional analysis of the feed samples was also performed.

Hoppe and Ulmer sampled rations from three pans: one each at the beginning, middle and end of the bunk line. They sorted each pan and counted the candy markers to determine whether the candy was evenly distributed. If not, the mix was not uniform, and changes would need to be made to ensure all animals received a proper ration mix.

They then calculated the CV (a measure of the extent of variability in relation to the mean) for components of the feed mix. In a properly mixed ration, the CV values should be low, indicating uniformity.

The CV was measured for the candy, dry matter, crude protein, acid detergent fiber (ADF), calcium and phosphorus, as well as for sample weights. Throughout the study, the candy was found not to be evenly dispersed, indicating room for improvement in mixing techniques. However, the CV of the nutritional components – ADF, crude protein, calcium and phosphorus – was found to be less variable and, in most cases, still adequate in meeting basic nutritional needs.

Precision feeding

Perfecting the feed mix may have a larger impact in some types of operations, such as a dairy farm, where milk production is closely tied to nutritional analysis of the total mixed ration (TMR). The nutritional needs of other livestock may not be as precise. However, ensuring that all animals are receiving the intended nutritional benefits and that the ration is uniform and consistent keeps feed costs in check by increasing feed efficiency.

Throughout the study, the candy was found not to be evenly dispersed, indicating room for improvement in mixing techniques. However, the nutritional components were found to be less variable and, in most cases, still adequate in meeting basic nutritional needs.

Ulmer said, “If feeding stock cattle, then a perfect mix may not be as important, but when feeding calves you want each mouthful to be the same from the first bunk to the last bunk filled.”

In his paper “TMR Delivery and Variability on the Farm,” Buckmaster wrote: “When considering mix uniformity, there are two distinct types of variation: variation among similar batches and variation within a single batch. Variation among batches is controlled by monitoring feedstuff characteristics and using proper formulation and weighing. Within-batch variation is controlled with proper mixer operation.”

Forage nutrient content can cause variations in nutrient concentrations among TMR batches. Forage moisture levels also cause variations. Dry matter intake needs to be adjusted as forage water content changes, but often is not.

“Of course, inconsistent weighing … of forages will always happen,” Buckmaster said. “When this happens, portions of the other ingredients should be adjusted accordingly to keep the ration correct.”

Within a batch, however, problems arise when the mixing isn’t optimum. Chemical analysis of ration samples helps to determine if both grain and forage-based rations are being properly incorporated. Regularly sampling the mix and having a chemical analysis done to monitor mixer performance can be a worthwhile investment.

Buckmaster recommends sampling the bunk in 10 places per batch when using tracers. Whole cottonseeds can make good tracers, he said. If you do need more consistency in the batch, try adding the feed ingredients in a different order, or try adjusting mix times and repeat the tracer study.

There’s another reason to get the ration properly mixed. In a research trial performed at the Carrington Research Extension Center, cattle were either fed ration ingredients separately or fed the same ingredients and proportions in a properly mixed TMR.

“Cattle gained more on the same amount of feed when it was a totally mixed ration,” Hoppe noted. “Presumably, fermentation is more efficient when feeds are mixed well. The goal is that when every mouthful of feed is the same, fermentation is more efficient.”

Wet feeds coated the candy, which made the Good & Plenty hard to find. The candy was much easier to find in dry feeds.


“If the mixer is not mixing the ration adequately, then repair may be needed. Mixers tend to look fine on the outside, but will show neglect of maintenance in the mixing chamber,” Hoppe said. “Repair or replace broken or bent blades, cutters, sweeps and mixing arms.”

Ulmer and Hoppe found that one of the biggest factors contributing to improperly mixed rations during their study was the upkeep and proper functioning of the mixer. While a mixer might be functional, that doesn’t mean it’s functioning properly.

“For the most part, poor maintenance was a problem,” Ulmer said. “Making sure the mixer is well-maintained and in good working order is key. If the mixer is in good working condition and has been tested but it can’t perform, then it may be time to upgrade.”

If you’re adding ingredients and filling the mixer properly, and there are no maintenance issues causing variations, but the mix is still not consistent within a batch, it’s time for a change.

“The mixer may not be designed for your rations, and a different mixer may work better,” Hoppe said.

Older mixers may work fine, Buckmaster said, as long as they’re properly maintained. Basic maintenance includes calibrating the scales and adjusting the knives, wipes or sweeps and anything affecting the clearances in cutting or cleaning aspects of the blending. Buckmaster recommends increasing energy efficiency by leaving the mixer off, or running slowly, when mixing ingredients. He said this simple step can extend the life of a mixer. It will also decrease particle size reduction.

“If mixing for four minutes is adequate, but the mixer is operated for six minutes while filling, four minutes for blending, and four minutes during unloading, there are 14 minutes of operation. If the mixer could be off during filling, then eight minutes of operation is enough,” Buckmaster said. “The change could dramatically influence mixer wear and life, and hence cost.”

Selection factors

Choosing a mixer that’s designed to accommodate your feed ingredients is a good first step. Select for the actual mixing capacity, rather than the size of the mixing tank. When deciding what capacity is right for your farm, consider the number of livestock, the density of the ration and the number of daily feedings.

“Size considering both the largest and the smallest batch you intend to make,” Buckmaster advised. “If you are making some small batches, reel and auger mixers will perform better than vertical mixers.”

The purpose of a feed mixer is to blend feed ingredients – no matter the particle size, density or water content – into a uniform, consistent mixture. In the real world, 100 percent uniformity does not exist. However, by using the right mixer design for your feed ingredients, mixing in the proper order and for the right length of time, and keeping your equipment maintained, you can make your mix as uniform as possible.