Optimal animal feed mixer for cattle, poultry, pigs, etc.

Copyright by amixon®, copying, reprinting, translation into other languages - even in part - only with the written permission of amixon GmbH, Paderborn.

A question of safety and mixing quality

The times when farmers fed their cattle and pigs completely from their own production with grass, hay, grain, beets and silage are long gone. The animal feeds produced by the farms themselves are now only used as "basic feeds". They are supplemented by the indispensable, so-called "concentrated feeds". This term refers to all animal feeds with increased nutrient concentration and other additives. In turn, a distinction is made between single feeds and mixed feeds. Single feeds with a high nutrient concentration include fats, soybean meal and molasses chips, a residual product from sugar beet processing.

A mixture of just two single feeds is already called a mixed feed. However, modern mixed feeds are in fact highly complex compounds that are composed of several single feeds and selected additives and thus individually cover the specific, current nutrient requirements of the different animals. A typical mixed feed today consists on average of eight to twelve single feeds and up to 15 additives. The most important single feeds in terms of quantity are the various grain types such as wheat, barley and corn, followed by rapeseed and soybean meal. Animal feed additives are minerals, vitamins, amino acids, trace elements and enzymes.

According to current figures from the German Farmers' Association, feed mixtures account for around 14 percent of farm animal feeds in Germany. Basic feeds account for 54 percent and single feeds for 32 percent. According to the German Animal Nutrition Association, the animal feed industry produced 24.1 million tonnes of mixed feeds in 2020 – 9.8 million tonnes for pigs, 6.9 million tonnes for cattle and 6.4 million tonnes for poultry.

The German animal feed industry is dominated by medium-sized companies. At the end of 2020, there were 287 mixed feed manufacturers with sales of 6.8 billion euros. There is a focus on North Germany. In the south, the demand for mixed feed is lower because animal stocks are lower.

Trend towards individual feed mixtures

Even though the industry is dominated by medium-sized companies, mixed feed formulations are being further developed with scientific commitment. A distinction is made not only according to the type of animal, but also according to the intended purpose, development level and performance capacity of the animals. Differences in nutrient requirements, digestive systems and metabolic mechanisms must also be taken into account. After all, it must also taste good to the animals and get from the silo truck to the day silo and from there without segregation to each individual animal. Hence, it is not uncommon for a single manufacturer to offer several hundred different recipes and formulations of mixed feeds.

In cattle farming, there are specifically tailored mixtures for calves, young cattle, dairy cows, fattening bulls and dry cows (cows in the phase between two calvings). In bull fattening, for example, the requirements are: high daily weight gains, a lot of muscle meat, low corpulence, a healthy bovine stomach and few illness-related losses. However, the basic feed usually has too few proteins for rapid muscle building. There is also a deficiency of minerals, vitamins and trace elements in the basic feed. A correspondingly designed mixed feed for bull fattening compensates for these deficiencies.

Modern farmers first have their self-produced basic feed analysed in order to determine the exact concentrations of nutrients (carbohydrates, fats and proteins), minerals (calcium, sodium, magnesium, etc.) and trace elements (zinc, copper, iodine, etc.). The mixed feed composition is then precisely matched to the farm-specific basic feed.

Although the basic feed analysis is initially associated with costs, these are usually quickly amortised, since the individual feeding makes the livestock farm more cost-effective. This is because all unnecessary minerals and trace elements contained in the mixed feed are cost drivers.

Precisely adjusted feed for animal welfare and environmental protection

Flexible, adapted animal feed production also makes adaptation to extreme weather conditions possible. For example, dairy cows can suffer from heat stress on summer days. Starting from an outside temperature of just 24 °C, the animals begin to feel less well, they eat less and finally give less milk. In a summer heatwave, the addition of sodium carbonate to the cow fodder is helpful.

A finely adjusted feed mixture can even contribute to environmental protection. Regular fertilisation of agricultural land is a must for high yields. Liquid manure is basically a good fertiliser if applied correctly and moderately. However, a lot doesn't always help a lot. Sometimes its phosphate and nitrogen inputs contaminate our drinking water. Dairy cows need a sufficient supply of phosphorus. Phosphorus deficiency leads to a reduction in feed intake, milk yield and fertility. If too much phosphorus is supplied, the dairy cow reacts with increased phosphate excretions. Cleverly balanced component compositions therefore also determine the quality of the liquid manure as fertiliser and help to protect both arable land and groundwater. For example, the animal feed manufacturer Agravis offers a ration calculation tool under the name "Phokus", which makes a targeted reduction of the phosphorus content in the feed possible.

© by amixon GmbH - amixon® HM 16000 mixer. Mass flow up to 70 t/h mixed feed for pigs, poultry and cattle

Requirements for animal feed mixers

When mixing the animal feeds, the homogeneous distribution of the individual components is crucial, because the individual animal only gets a minimal fraction of a batch and this fraction should ideally have exactly the same composition for every animal on a farm. This also applies to each individual feed ration, even if some trace elements were only added to the mix in extremely small quantities. Animal feed mixers should be suitable for evenly distributing very small mass fractions in ground grains. In the industry, the requirement for the quantity composition is formulated with 1 in 10,000 to 1 in 100,000. This is a requirement and by no means a measure of the mixture quality.

Animal feeds are mass products and the manufacturers produce them with very low profit margins. In this respect, a further requirement is that the dwell time of the mixtures in the mixer should be as short as possible – even in the factory. It is not uncommon for the mixing duration of a batch to last only four to six minutes. The feeding of the mixer with all the components involved in the recipe, the mixing, the emptying of the mixer and the closing of the emptying device all take place during this time. With a 12 m³ mixer, such a short mixing cycle requires specific mixing machine characteristics.

The interaction of, for example, recipe development, component provision, component weighing, the homogenising capability of the mixer and the intake capacity of the subsequent units requires an enormous amount of know-how on the part of the user. Ultimately, the energy balance must also be right. Every unit for in-plant bulk material logistics and product processing must be supplied with electrical energy, is subject to wear and tear and makes mixed feed more expensive.

Demonstrating product safety and mixing quality

In view of the large number of components and the constantly changing recipes, the logistical performances of animal feed manufacturers are excellent. Raw materials whose daily price seems inappropriate or which are not available on the market often have to be substituted by others with comparable nutrient contents...

These are the requirements for the mixer as a value-adding device in the production chain:

  • Achievement of ideal mixing qualities that cannot be improved upon in practice

    • within a short time and

    • with variable filling levels

    • with minimal energy input and

    • best possible resistance to wear

  • fast and complete emptying, ideally within a few seconds

  • long service life

  • good accessibility and cleanability of the mixing chamber

  • ergonomically reasonable entry to the mixing chamber

  • Simple repair of worn components – ideally by the user's own fitters, who have been specially trained beforehand.


Based on Regulation (EC) No 178/2002, the animal feed manufacturer is responsible for the safety of the animal feed along the entire chain from the primary feed production to the feeding of animals for food production. This safety is ensured by the animal feed manufacturer by applying the HACCP principles in conjunction with good hygiene practice.

Industrially operating animal feed companies have established their operating procedures in an audit-proof manner. Each individual batch can be tracked without gaps.

The Animal Feed Hygiene Regulation (Regulation (EC) No 183/2005) supplements and deepens these general regulations. Among other things, it requires the companies to prove the effectiveness of their mixing plants in terms of homogeneity. These proofs are provided on the basis of practical expert appraisals carried out under normal operating conditions. The experts orientate themselves to the guidelines for checking the work and mixing accuracy of animal feed companies (https://www.bmel.de/SharedDocs/Downloads/DE/_Tiere/Futtermittel/Leitfaden-Arbeitsgenauigkeit.html) in the current version from 2018.

In practice, the mixing quality is to be regarded as equivalent to the homogeneity of a mixture.
It describes the ability of a mixing plant to "mix different amounts of individual components homogeneously
with one another in a defined time".

The determination of the mixing quality of a heterogeneous bulk material is a complicated process engineering challenge. There are more than 20 different equations to define mixing qualities. Practice-oriented methods have been established to verify the mixing quality for animal feeds. Organic food dyes or microtracers are added to the animal feed in a ratio of 1:10,000 – equivalent to one hundred grams of active ingredient per tonne. After a defined mixing time, a sufficient number of samples (but usually at least ten) with a sufficiently large volume (in practice often 20 g – the ration for a chick) are taken from different locations of the mixing chamber by means of a sampling device and analysed. The quality of the determined mixing quality analysis depends on many parameters, but in particular on the number of samples and the selected sample volume. It is particularly important to divide or portion samples in such a way that they do not segregate.

Challenging situations always arise when a completely new type of product or process is to be established or when a new mixer is put into operation, because the mixed feed manufacturer will then want to know how the homogeneity develops over the course of the mixing time and how long it has to mix in order to achieve a sufficiently high mixing quality. To find out, the procedure below can be followed:

According to the above description, the sampling is repeated after further short mixing phases. For example, the first ten samples are taken after about 180 seconds, and the second ten samples after another 40 seconds of mixing time.

In the case of an amixon® mixer established in operation, the universal mixing efficiency is considered validated. In this respect, it is then sufficient to take the samples during mixing by means of a dead space-free sampling valve with the mixing tool rotating. This also applies to retained samples.

The particle size distribution also plays a role in obtaining a high mixing quality. Experience has shown that minor components can best be homogenised in the basic feed when their particle size is between 200 and 500 microns. Particles that are substantially smaller are more difficult to dose and control. They can accidentally get into the dedusting filters or randomly aggregate on larger particles, thus making homogeneous distribution difficult.

In order to verify that any cross-contamination from batch to batch is excluded or takes place below the detection limit, the procedure below is followed: The previously used mixer is reloaded with the ground raw materials without manual cleaning. A mixing cycle is then run. Analogous to the above description, samples are taken and examined for the microtracer or dye. Ideally, the tracers or dyes should not be analytically detectable in pure animal feed.

These verifications should be carried out every ten years. In the case of premixes, the verifications should take place every five years. In practice, the verification should take place not only for the mixer, but for the complete process from the batching scales to filling.

Selection of a suitable mixer

Precision mixers – whether with horizontally or vertically rotating mixing tools – meet the mixing quality criteria for animal feed mixtures without reservations. However, there are major differences in

  • the mixing time,
  • the flexibility of the filling level,
  • the degree of residue-free emptying,
  • the cleanability/accessibility,
  • the emptying speed and
  • the power requirement of the drive.  


In order to select a suitable mixing system, the space requirements of the mixers must be coordinated with the space available on site. amixon® can customise its mixers; from a low, flat version to a slim version when the available footprint is small. In addition, amixon® can also produce any desired size in 100 litre steps. Otherwise, the aforementioned criteria "Requirements for the mixer" apply. Common batch volumes in the animal feed industry range from two to six tonnes (about 4 to 12 m³) and for mineral mixtures one to three tonnes (about 1 to 3 m³).

Targeted dosing of liquids and homogeneous distribution

Animal feed mixtures also contain a wide variety of liquid additions such as fat, water, amino acids, molasses or vitamins - just as much as the farm animals need. In addition, the dust content should be bound and the taste improved.

As a rule, powdery feeds are only enriched with small quantities of liquid. If liquid admixtures are necessary, it is an important selection criterion that the mixer wets all particles as evenly as possible.

What is interesting in this context is that the porosity of the material increases slightly with the addition of a low quantity of liquid, the filling becomes looser and more free-flowing, the volume of the mixture increases slightly, the dust content decreases and the flowability improves slightly. But it is not a trivial matter to quickly and homogeneously wet a bulk material with a wide particle size distribution.

Surface tension; affinity between liquid and powder

a.     The surface tension of the liquid is low, so that it quickly penetrates and wets the structure of the hydrophilic solid. This is comparable to a superabsorbent granulate that absorbs spilled oil.

In this case, the uniform distribution of liquid only works by spraying – if possible – all surfaces of the powder with the same amount of liquid. The homogenisation of a previously non-homogeneously distributed liquid phase by subsequent intensive mixing is no longer possible. At the most, diffusion can help here to homogenise the liquid phase. As is well known, however, diffusion takes a long time, allows the mixtures to clump together and is therefore not a good solution.

b. The surface tension of the liquid is high and the powder has a hydrophobic surface, similar to the lotus effect.

In this case, the homogeneous distribution of the liquid phase can only be achieved by deagglomerating mixing – i.e. with mechanical distribution work.


Viscosity of the fluid

In addition, the viscosity of the liquid is significant. The lower the viscosity of the liquid, the better it can be sprayed. Consequently, there are advantages in adjusting the viscosity appropriately. Since the viscosity usually decreases with increasing temperature, it makes sense to heat both the liquid and the pipeline and the lance for the liquid addition. However, the viscosity does not change immediately after a temperature change, but only after a slight delay.

Depending on the type (dilatant, Newtonian or structurally viscous), liquids behave differently when they are sheared. Shear stress is triggered, for example, when a liquid is mixed or pumped at high speed, when it flows quickly through pipelines or when it is sprayed. For example, if one were to try to convey a dilatant liquid with a centrifugal pump or to inject it into the mixture with a nozzle, then its viscosity would increase. The dilatant liquid introduced in this way can then only be distributed in the powder with difficulty. It is much more likely that it will form many small moist granules that are ultimately no longer dissoluble.

Amino acid additions in liquid form such as aspartic acid, glycine, methionine, tryptophan, lysine, threonine or valine tend to behave in a dilatant manner.

A structurally viscous liquid, on the other hand, reacts to shearing in a completely different way: Its viscosity is reduced, and pumping and spraying therefore significantly support distribution.

Water and cooking oil, on the other hand, exhibit Newtonian behaviour. They maintain their viscosity to a large extent – regardless of any shear effects. This also applies, for example, to many aqueous solutions.

If the homogeneous distribution in the mixer causes problems, certain liquid amino acids can also be obtained in a powdery consistency. In most cases, however, the powder form is more expensive and its addition is less easy to automate.

Post-treatment below the mixer can shorten the process time

If the cycle times are very short, all liquid additions must be pumped into the mixer correspondingly quickly. After a short mixing time, the amixon® twin-shaft mixer contains a homogeneous product. However, isolated agglomerates (diameter 2 to 5 mm) may still be present. Although these wet agglomerates are homogeneously distributed throughout the mixing chamber, they are not yet completely dispersed in the mixed feed. In order to distribute them completely with the high-speed cutting rotors, the mixing process would have to be extended, even though the mixing quality has already been achieved. In this case, a post-treatment method has established itself as more energy-saving.

In order to completely crush agglomerates, it makes sense to install a so-called finisher below the mixer. The mixture passes through the finisher continuously at a high flow rate. The specific energy input is minimal. Even in the smallest volume, all liquid components can then be detected in the correct composition.

Two different forms of liquid addition in the same powder mixer

The picture below shows the lower end of an amixon® conical mixer with two different systems for liquid addition. On the right you can see how the liquid is injected into the active area of the high-shear unit with a single-component nozzle. The liquid material is distributed here by shearing and deagglomeration.  

The mixing cycle does not always have to be so fast. The liquid substances can then be injected into the mixture or finely sprayed.

© by amixon GmbH - Two methods of adding liquids to the powdery mixture

On the left you can see a two-component nozzle. The pressurised gas introduced into the mixing chamber atomises the liquid into microfine droplets and at the same time fluidises the mixtures as they flow past in the target area of the nozzle. The gas turbulence creates a fine, wetting mist. This makes it possible to distribute very small amounts of liquid homogeneously in large powder batches. The mixture bed acts like an absorber for the rising mist. The fluidisation gas leaves the bulk material at a greatly reduced speed. The bulk material bed acts as a dust and liquid absorber.

Both processes, the particularly gentle two-component process (left) and the "heavy-duty method" (right), can take place either optionally or simultaneously in the same mixer. This conically designed amixon® mixer also tolerates strongly fluctuating filling levels.

amixon® is synonymous with precision mixers with vertical mixing tools

A helical mixing tool, which is driven and mounted centrally, exclusively at the top, rotates inside a cylindrical mixing vessel. The mixtures are fed from above, while the mixer is emptied at the bottom by opening a coplanar flap that seals to the level of the mixing chamber base. This is a dead space-free sealing flap that is opened and closed electro-pneumatically inside a neck. All components in contact with the product are carefully welded and ground, as is the mixing tool. Shovel-like arms carry the helix of the mixing device, which has been manufactured here in the "concave" form.

© by amixon GmbH

Optionally, the mixing tool can be fully heated, in which case both the mixing shaft, the arms and the helix of the mixing device are executed with a double sheath. The thermal fluid tempers the entire mixing tool. Steam, water or thermal oil can be used as thermal fluids. The mixing tool generates a three-dimensional continuous flow without dead spaces. Sometimes it is necessary to deagglomerate or to distribute liquid additives particularly effectively in the powder. The chopper tools or high-shear blades are then used; these partially release a high power density in the powder. The figure below shows the flow principle. In this respect, amixon® twin-shaft mixers are universally well suited for almost all product types. It is irrelevant whether the mixtures are granular, dusty, fibrous, dry, moist, pasty, liquid, free-flowing or poorly flowing. The mixing tool is designed in such a way that the entire content has been shifted once after about four to five revolutions. This flow principle is also called vessel flow. Usually all components are homogeneously distributed throughout the mixing chamber after a few revolutions; we speak of an ideal mixing quality that cannot be improved any further in practice.

The twin-shaft mixer shown below is a special case. It consists of two intermeshing single-shaft mixers. The mixing tools agitate far into the centre of the opposite mixing chambers. Twin-shaft mixers roughly halve the mixing time and the energy input and represent the premium class.

© by amixon GmbH - Twin-shaft mixer type HM und flow principle – three-dimensional shifting

Mineral mixtures

The so-called mineral preparations are a special form of feed supplement. They are added in small proportions to the mixed feed for the farm animals. The recipes are specially tailored to the needs of cattle, pigs, horses and poultry. These are lime and active ingredient mixtures that optionally contain iron, vitamin C, calcium, zinc, iodine, copper, selenium, chromium, fluorine, potassium, sodium, magnesium or phosphorus. Since they act as minor active ingredient components in the mixed feed, they must be particularly homogeneous and easily distributable. In order to make them dust-free, they are partially encapsulated or agglomerated. For these products, too, the aim is to achieve a lump-free and dust-free product with the highest mixing quality.

Regardless of which amixon® mixer is used – a single-shaft mixer or a twin-shaft mixer – ideal mixing qualities are achieved in every case. The two mixer designs differ only by the required mixing time and the associated energy input.

If the energy input is to be minimised, there is no alternative (except for the KoneSlid® mixer) to the twin-shaft mixer: It

  • achieves a particularly gentle flow of the mixture with minimal energy input
  • has a low and particularly compact design
  • can cope with varying filling levels
  • has particularly good accessibility and is ideally manufactured hygienically
  • is suitable for all types of dry, wet and suspended goods
  • can achieve particularly good residue-free emptying
  • can optionally also have several discharge nozzles
  • has – like all amixon® mixers – a mixing shaft that is mounted and driven only at the top.

Milk replacer

If the calves are separated from the suckler cows at an advanced age, the udder of the suckler cow is no longer available for feeding. Special dried milk derivatives are enriched with fat, trace elements and vitamins. The finished mixture is packed in small containers. The goods are then suspended or dissolved in water as required, and are particularly nutritious for the young animal.

© by amixon GmbH - amixon® HM 4000 mixer with particularly large discharge fitting

© by amixon GmbH - amixon® conical mixer type AM

amixon® conical mixer

Since the conical mixer can mix quickly and empty quickly and completely, it is conveniently used as a so-called END-OF-THE-LINE mixer. The conical mixer then empties directly into the silo vehicle or into the filling machine. The focus is on its ability to ensure absolute freedom from contamination in the production of so-called medicinal mixtures. Residues of the previous batch must under no circumstances be carried over into subsequent feed mixtures. The conical mixer is therefore often located at the end of a production chain. The medicinal components are dosed directly into the mixer, distributed homogeneously in the mixed feed and then completely discharged into the end user container.

 

The requirements here are:

  • ideal mixing quality,
  • short mixing time,
  • excellent, thorough, residue-free emptying,
  • fast emptying,
  • large inspection doors – good accessibility and
  • particularly hygienic design.

In addition, this mixer has a further speciality: It can be operated either batchwise or continuously.

© by amixon GmbH - amixon® AMK 400 continuous mixer

© by amixon GmbH - amixon® AMK 10 000 continuous mixer; mass flow up to 120 t/h

Functional description of the continuous mixer type AMK

The discharge device of the mixer is closed at the start. All the gravimetrically working dosing devices are started simultaneously with a small mass flow and tune themselves automatically to one another. Any dosing errors are also corrected from the start of dosing. The filling level of the mixer increases continuously; the mixer drive only starts at about half the filling quantity in order to protect the mixture.

When

  1. all dosing devices have reached their stationary operating point and
  2. the input according to the recipe has been reached and
  3. the desired filling level in the mixer has been reached,

    the discharge device opens slowly and the ideally mixed product is continuously discharged from the mixer. Optionally, the dosing flows can now be increased while constantly tuning.

    Right from the first gram to the end of the mixing procedure, only ideally mixed product is produced. Typical dosing fluctuations at startup are corrected by the system itself. Any unintentional dosing fluctuations are compensated in the best possible way.

    The amixon® AMK 10000 continuous mixer shown above rests on load cells and the conveyors installed above it are highly accurate gravimetric dosing systems. If the mixer is operated continuously, it can produce up to 120 t/h. However, the mass flow can also be reduced to 20 t/h. If the same mixer is operated batchwise, it can ideally and accurately mix batches of varying size from 1 m³ to 10 m³.

    This may be necessary, for example, if small orders have to be fulfilled or premixes have to be produced from a particularly large number of components, which are then to be distributed in the final mixtures in the continuous process.

    The following checklist can help you to decide whether a continuous or batchwise mixing process is preferable in a future case.

    A continuous mixing process is usually advantageous

    • if a short, defined dwell time is required; e.g. defined deagglomeration, spontaneous build-up granulation with liquid addition, or spontaneous chemical reaction with heat dissipation;
    • if the recipes are standardised and the qualities of the components are assured;
    • if the recipe consists only of a few components;
    • if large quantities of the same or similar product are produced, possibly even in three shifts (bulk goods such as basic nutrients in grain mills);
    • if a high degree of automation is required.
    • Modern productions today are largely automated. As a rule, the automation of a continuous mixing process is simpler.

    A batch mixing process is advantageous

    • in the case of complex preparation procedures, such as multistep mixing operations or mixing operations with the application of overpressure or vacuum;
    • if the properties (such as colour, consistency, viscosity, particle size) of the individual components change, the mixing is analysed before filling and, if necessary, components need to be mixed in subsequently;
    • if there are many components in the recipe;
    • if individual mixing orders are concerned and the recipes change frequently;
    • if 100 % batch control must be performed.

    However, the decision is always individual – often in the context of the company's history, the industry, the customer and order structure, the competitive environment and the strategic orientation of in-house developments. The decision-making aids listed therefore cannot be claimed to be exhaustive. Depending on the application, many other criteria can play a role and any disadvantages should be addressed and weighted equally when planning a new greenfield plant.

    Extremely fast mixing and emptying with the KoneSlid® mixer

    In the selection of a mixer, a new development from amixon® should be mentioned: a conical mixer with a special emptying device. This amixon® mixing machine also ensures ideal mixing qualities. It can be used wherever a particularly fast batch change with minimal cycle time and fast, residue-free emptying are required. With the KoneSlid® mixer, cycle times of three minutes are the rule rather than the exception.

    © by amixon GmbH - amixon® KoneSlid® mixer KS 400 with complete discharge in seconds

    amixon® Gyraton® mixer for particularly large batches

    Another new development from amixon® is suitable for particularly large batches. This mixer bears the name Gyraton®. It is used for the gentle but precise homogenisation of large individual batches of the same product. The raw materials are often delivered in containers. Up to 70 m³ of mixture can be transported in a 40-foot container. The goods delivered may be different batches of the same goods. Sampling for the purpose of quality determination is therefore not possible as long as the goods are inhomogeneous.

    High mixing silos or conical mixers with orbitally moving mixing screws are traditionally used for the purpose of homogenising large batches. In contrast, a Gyraton® mixer for 70 m³ batches has comparatively compact dimensions with a height of 8.7 m.  It can handle all filling levels up to 70 m³ and can also be conveniently entered and inspected.

    A Gyraton® mixer has a comparatively small drive; the power consumption is low. In return, the mixing process takes a little longer. The helix of the mixing device conveys the mixtures upwards in the familiar way and allows them to flow downwards through force of gravity. The effective diameter of the helix tapers downwards.

    In order to reach all areas of the mixing chamber despite that, the rotating mixing tool gyrates so that the helix glides along the entire wall.

    © by amixon GmbH - amixon® Gyraton® mixer; low drive power for efficient, gentle large batch homogenisation

    Bulk materials behave in a significantly different manner to liquids. The pressure of a water column increases in proportion to the filling level and remains almost constant, even when the mixing tool rotates. If there is a bulk material in the mixer instead of water, then a large part of the bulk material load is borne by the friction on the cylinder wall. However, this changes abruptly when the mixing tool rotates. The friction force of the particles against the cylinder wall is consumed and the dynamic pressure increases. The dynamic pressure counteracts the movement of the mixing tool. This dynamic pressure increases disproportionately with increasing filling height. Therefore, particularly large drive torques are normally necessary.

    The situation is different in the Gyraton® mixer. The diameter of the mixing helix is tapered and corresponds to only half the vessel diameter at the bottom. The drive torque and circumferential speed are halved at the point of the maximum dynamic pressure, which is why the drive torques are also lower.

    The requirements for an animal feed mixer can differ significantly depending on the type of mixed feed manufacturer.

    Therefore, the operating and production situation must be thoroughly evaluated before purchasing a mixer.

    Requirement criteria could be, for example:

    • Strongly varying filling levels occur / do not occur
    • Preservation of particles when mixing is necessary/unnecessary
    • Liquid distribution required even with a low filling level/ ....
    • Particularly gentle liquid distribution necessary/ ....
    • Intensively deagglomerating and particularly fast liquid distribution should take place/ ....
    • Very fast residue-free emptying required/ ....
    • Slow or cycle-wise portioning emptying desired/ ....
    • Best possible residue-free emptying/ ….
    • Emptying into several filling machines optionally or simultaneously required/ ....
    • Lowest possible power consumption required/ ....
    • Special wear protection required/ ....
    • Mixer is also to be used for process and product development and is therefore particularly versatile in use/ ....
    • Production is predominantly mono production/ ....
    • Different mixing orders should be carried out in quick succession/ ....
    • Ergonomic accessibility required for fast dry cleaning/ ....
    • Fast wet cleaning and drying should be done frequently/ ....
    • Liquids should be impregnated in pellets/ ....
    • Pressure- or vacuum-tightness of the mixing chamber required/ ....
    • Finished mixture has different bulk densities from .... kg/dm³ up to .... kg/dm³
    • Mixtures should be tempered in the mixer/ ....
    • Gas should be injected in the mixer/ ....

    amixon® synthesis reactors (flat or conical base)

    In order to complete the selection, the two pressure- and vacuum-resistant amixon® mixers with double jacket should also be considered. Appliances in this design are of interest

    • if an organic product is to be sterilised with saturated steam;
    • in the preparation of penicillins, or
    • when enzymatic fermentation or
    • vacuum drying takes place;
    • if porous bulk materials (pellet extrudates) are to be impregnated pore-deep with higher viscosity liquids. (The application of a vacuum makes the pores gas-free; light pressure build-up stabilises the impregnation)

    © by amixon GmbH - amixon® vacuum dryers, synthesis reactors

    amixon® Test center in Paderborn

    All the precision appliances presented can be extensively tested in the amixon GmbH technical centre. On request, the test mixers can also be used for on-site tests at the customer's location. Top results are guaranteed in advance, as well as a high gain in knowledge with deeper insights into the processes of modern apparatus construction.

    - © by amixon GmbH - amixon GmbH manufacturing program

    Statements of various owners of medium-sized animal feed businesses:

    What differences do you see in animal feed production/mineral processing or the production of pet food?

    Food for farm animals is much more important as a commodity and also has correspondingly higher sales than, for example, pet food, because food for animal nutrition is the most important commodity for agriculture, as farmers usually derive most of their income from the sale of pork, beef, poultry, milk and eggs. Mineral mixtures do not consist of nutrients such as starch, sugar, fat and proteins (amino acids), but instead contain inorganic elements such as calcium, magnesium and phosphorus compounds, as well as the necessary trace elements. These include metal salts and compounds such as iron fumarate, copper sulphate and zinc oxide. Iodine and salt (NaCl) are also trace elements that are often not contained in optimal quantities in grains – the natural raw materials for feeds.

     

    Are animal feeds produced in Germany different from those produced in Europe or the USA?

    Basically, everyone is striving for the same optimal values. However, these are achieved through a different mix of components, because in southern, warmer countries, protein- and fat-rich raw material plants such as soy and peanuts thrive better than in cooler zones of the earth. Here in Central Europe, on the other hand, we have very good grain soils and sufficient rainfall. Our yields per hectare of grain are significantly higher than, for example, in the USA. Europe therefore exports more grain than the USA. Conversely, we import more protein components. The formula for fattening cattle fodder in the USA is "grain plus soy plus minerals", while for us it is more like "grain plus soy plus rapeseed plus amino acids plus mineralisation". In this respect, there are indeed regional differences.

     

    High-quality raw materials are needed for high-quality animal feeds. How do animal feed producers solve this challenge?

    Due to the high performance of modern combine harvesters, the harvesting time has been reduced from several weeks to a few days. Even rainy summers have at least some, if only a few sunny days, so that grains can usually be harvested dry. Dry storage benefits the quality of the deliveries from the immediate vicinity.

    High-performance wholesalers, brokers and importers often specialise in a few core components and help to avoid bottlenecks. The availability of good qualities is therefore not a big problem in most years.

    The problem for everyone is rather the most favourable time to complete the purchase, because prices are often highly volatile.  

    On the subject of quality, it should also be mentioned that the grain is cleaned immediately after delivery by wind sifting, as well as heavy and large part selection. A few companies use the particularly effective drum screen cleaning, with which the grain can be freed from unwanted adhesions such as sand, soil and especially microorganisms.

     

    Almost exclusively physical processes are used for animal feed production: separation based on particle size differences or density differences, cleaning, mechanical crushing, mixing, pelletising and, if necessary, impregnation. Are fermentation processes ruled out due to excessive dwell times and costs?

    No, not directly. Dry processing is preferred mainly because of the better storability. In addition, many farmers process their own grain themselves. This is much easier in the dry state, so that fermentation processes for animal feed preparation are out of the question.

    Chilled grain can be stored in the long term with a moisture content of up to maximally 13 percent. Wetter feed and feed components spoil very quickly. This process can be slowed down (within limits) with the help of propionic acid.

     

     

    Where do the differences in animal feed quality originate?

    The process chain starts with the quality-conscious purchasing of the components. The qualification, experience and further training of the employees entrusted with the optimisation of the feed recipe are particularly important, because many quality criteria cannot be expressed in numbers alone.

    Optimally suitable and reliable production machines are also necessary for: cleaning, sieving, weighing, grinding, mixing, pressing and granulating – everything has to work optimally. The result is ultimately shown by success in the cowshed.

     

    Do particle shape and size also play a role in animal feed quality?

    Naturally! It has been scientifically proven that the way in which the raw materials are crushed significantly influences the digestibility and thus the health of the animals. If particles are crushed, their surface area increases and the digestive and metabolic mechanisms benefit from that. However, fine portions in the grist are undesirable, as these can lead to gastritis and ulcers in pigs.

    While a classic hammer mill effectively crushes the grain, it rounds the fracture edges of the particles. If, on the other hand, the crushing is done with a double crushing roller mill, the fracture and shear edges are retained in the crushed mixed feed. What's more, the dust content is significantly reduced. In this respect, the process technology of crushing contributes to a healthy gastrointestinal tract of farm animals. A double crushing roller mill also provides a particularly uniform grain size distribution, which is particularly important for poultry feeding. As you can see, even the type of raw material crushing influences the animal feed quality.

     

    To what extent does the mixer contribute to animal feed quality?

    We expect mixers to work gently, too, so that they do not round the fracture edges of the particles and do not produce any additional fines, because this contributes directly to the health of the farm animals. It is also crucial that the mix that leaves the mixer is ideally homogeneous and has not been heated.

    Since we run many different mixing orders one after the other, the residue-free emptying of the mixer and that of the system are also an important quality aspect. 4.5-tonne batches must be completely emptied to at least 1000 g in a few seconds. This kilo then corresponds to 0.22 parts per thousand residue and means that the batch was mixed practically without carry-over.

    In addition, energy consumption is an important quality feature for us. The more effectively the mixer works, the shorter the mixing time.

     

     

    What route will animal feed companies take in the future? Do you see any trends?

    Nutrition is the most urgent basic human need. In the future, animal feed companies will focus even more on sustainability.

    The structural change in the German agricultural industry will also have a lasting impact on the animal feed industry: in the future, it won't just be about more output, but also about higher quality.

    In addition, effects of the animal welfare debate are to be expected. Animal feeds can make a significant contribution to animal welfare. They can also reduce the environmental impact of animal husbandry and contribute to nature conservation. There are excellent ways to reduce nitrogen (N) and phosphorus (P) excretions via the feeding. This is good for the farmland and protects our drinking water.

    In the future, consumers will also expect GMO-free raw materials from us, as well as fully degradable pesticides and mineral fertilisers.

     

     

    What changes are you observing in the structure of your agricultural customers?

    Overall, the number of farms – and also of fattening farms – is declining. The trend towards large farms (+ 35 % between 2010 and 2019) continues unabated, but the number of small and medium-sized fattening farms is decreasing.

    Although the size of large farms continues to grow, they cannot fully compensate for the trend. We are therefore recording a slight negative trend in German animal populations overall.

     

    Which raw materials do you use for animal feeds and where do they come from?

    By-products from starch production are used in animal feed production. These include Maisarin (corn gluten, a by-product from the manufacture of starch from corn that contains proteins), wheat bran and wheat feed flour (wheat starch) as well as distiller's dried grains. (Distiller's dried grains are a by-product from bioethanol production).

    By-products from sugar production are also used as animal feed, for example, in the form of molasses and sugar beet chips.

    Science is trying to open up new sources of raw materials for animal feed mixtures. One alternative could be insects (e.g. locusts, larvae of the soldier fly) in animal feed. That's less creepy than it sounds, because insects are phenomenally efficient protein producers and could reduce our import of soybeans. Algae are also a possible alternative to soybean meal.

    Both alternatives are currently being tested. Natural enzymes are used to make the natural phosphates and non-starch polysaccharides present in the raw feed materials available to the animal.

    Other by-products from food production are also used in mixed feed production, for example, biscuit waste or rapeseed meal from rapeseed oil production or dried apple pomace, which results from the production of apple juice, as well as wheat bran, which is a by-product from wheat flour production.

     

    The nutrient content of the raw materials can no doubt vary with this range of raw material sources. However, knowing them exactly is surely a prerequisite for the optimal composition of the animal feed mixture, isn't it?

    That's right. Mixed feed manufacturers usually use near-infrared spectroscopy systems (NIRS) for this purpose. Infrared light in the frequency range from 800 to 2500 nm is shone through the nutrient sample. The frequency range of the absorbed and reflected radiation is measured. NIRS is an established analytical method for the ingredients of crops, dry matter masses, crude protein, crude fibre, crude fat and starch. Even a possible pathogenic infestation of the starting materials for the animal feed can be detected with a high degree of certainty.

     

    At critical times, a mixed feed manufacturer records the current prices and availability of all protein and energy sources several times a day and stores the data. A powerful optimisation program iteratively calculates the mixing result from these thousands of data sets and makes suggestions on how an animal feed recipe should be optimally composed. Purchase price, availability and the needs of the farm animals are taken into account as boundary conditions.

     

     

    How long is the shelf life of the animal feeds after production? Or should they be fed immediately?

    Normally, the mixed feeds are fed within a few days, so oxidation does not play a role. 99 % of customers receive their goods by silo truck. The best-before date is 3 months. As a rule, the goods are consumed within a few days.

     

    How important are analytics and consulting for farmers and animal feed manufacturers?

    Analytics and consulting play an important role for us, because only in this way can the feed be optimally adapted to the individual growth phases and farms. The quality of the feed can be optimally ensured and further optimised through frequent analyses and checks. In addition, individual mixtures can be created for each farm on request. Different animal breeds, for example, can place different demands on the animal feed. In practice, the farmer expresses his individual wishes to his advisor and then receives the optimal animal feed recipe for his farm. Many farms use by-products such as biscuit waste, bread and chocolate in addition to the farm's own grain. The respective quantities and ingredients are then also analysed by us in order to be able to recommend the appropriate supplementary animal feed.

     

     

    Many hundreds of tonnes of raw materials are delivered to animal feed manufacturers every day. Equally large quantities of animal feeds are transported away. No doubt the appropriate logistics for this are challenging …

    Our optimally adapted logistics are a prerequisite for performance and cost-effectiveness. This topic is constantly being put to the test.

    Most of the raw materials are delivered by third-party service providers (freight forwarders); some of the grain comes from local farmers. The rest is purchased.

    We deliver ready-made feeds and supplementary feeds to farms with our own vehicles and local drivers, who also perform informal secondary tasks and thus update and maintain the exchange of information with the farmer. If animal feed sales decline depending on the season, our own drivers are also used to fetch raw materials.

     

    What wishes or advice do you have for apparatus manufacturers, farmers or politicians?

    We would like the lowest possible energy consumption and a long service life of the systems from the machine and apparatus manufacturers. Many hundreds of thousands of tonnes of mixed feed are produced every year. That is why we attach great importance to wear protection.  

    Important spare parts must be available at fair prices in the shortest possible time. These include the right gearboxes, motors, timing belts, roller bearings, etc. In addition, we expect the apparatus manufacturer to carry out repair work – if necessary – even on Sundays and public holidays.

    The better our in-house fitters are trained by the machine manufacturers in terms of value retention and repair, the safer and better they can carry out the important maintenance and repair work themselves.

     

    What would you like to see from your customers, the farmers?

    Feed quality always pays off in the long term. It ensures good animal health and consistently good performance of the animals.

    Our daily production process would be easier to plan and more cost-effective if customers were to place their orders two days before the delivery date. The fulfilment of this wish would be advantageous for both sides.

     

    You already mentioned the animal welfare debate as an important criterion for future trends, but as a feed manufacturer, what are you looking for from politicians?

    Legal constraints and requirements for the husbandry conditions of farm animals must be uniformly regulated and checked in Europe. Market access must be prohibited for food not produced according to European standards. These two points are important for fair competition, because otherwise we will lose animal breeding and production in Germany.

    The consequence would be that we would have neither control nor influence over how our food is produced. For example? The keeping of battery hens has been banned in Germany for eleven years, but is still practiced in some EU countries today because it is much more cost-effective. This is completely unacceptable within Europe.

    Planning security is also important for farmers. Therefore, specifications for the required standards for the design of the stables must remain permissible after the legal entry into force at least for the depreciation period.

     

    Thank you very much for your statements, which have enriched our view of this important industry by many facets.


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