Personalised nutrition that provides the body with just the right nutrients, avoids obesity, reduces the risk of diseases and increases well-being: the dream of many nutrition-conscious self-improvers has long been implemented with scientific meticulousness in mixed feed for farm animals. Animal feed manufacturers are always looking for new ways to improve the benefits for agriculture through a sophisticated composition of feed mixtures. This includes, for example, highly developed animal feed compositions that protect groundwater by reducing pollutants in the liquid manure. However, the most important prerequisite for the effective feeding of farm animals is the ideal, uniform distribution of all the active ingredients in the feed.
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.
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.
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.
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.
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:
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 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.
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
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).
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 lightly. But it is not a trivial matter to wet a bulk material quickly and homogeneously with a wide particle size distribution.
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.
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.
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.
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 an ideal mixing quality in a very short time
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.
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:
In addition, this mixer has a further speciality: It can be operated either batchwise or continuously.
The following checklist can help you to decide whether a continuous or batchwise mixing process is preferable in a future case.
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:
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
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.