Role of Homogeneity in Premix

25 May 2020

The production capability and the technical know-how of compound feed factories varies worldwide, according to the production aim, type of equipment, age of feed mill, capital investment and maintenance & reconstruction. The feed is a solid mixture of macro-ingredients and micro-ingredients like vitamins, trace minerals, other feed supplements, feed additives medicaments and diluents. The micro-ingredients warrant addition at smaller inclusion levels in final feed (grams or milligrams per ton of feed) and hence need to be supplemented in the form of a premix, rather than addition of individual components onto the feed. Premix by definition is “mixtures of feed supplements/additives or mixtures of one or more feed supplements/additives with feed materials or water used as carriers, not intended for direct feeding to animals”.

The main objective of premix is to deliver the micro-ingredients in a manner as desired by the consumer. Process of premixing has undergone progressions over the several years starting with simple hand mixing of several ingredients to mechanical mixing, to continuous mixing, and now been automated computer controlled process. However, the basic concept of mixing ingredients together to result in a homogenous blend has remained unchanged, over the years, though the precision part has greatly enhanced with newer technologies. In the course of premix production, a key factor that is highly crucial for any successful premix production is to disperse the individual constituents as thoroughly as possible throughout the entire product to produce a homogenous mixture. In fact, homogeneity of the mixture is one of the most important features of the product, which need to be optimized not only for qualifying the mixture, but also for optimizing the technological process. Homogeneity of premix acts as a value added solution in enhancing the safety and quality of final feed. Production of premix is an art and should essentially be carried out by organizations that have an expertise in micro-ingredient handling.

Premixing of micro-ingredients with a suitable carrier is a common method used to achieve homogenous distribution of these nutrients in the final feed. This dilution  must  be  carried out accurately  and  carefully  under  a  strict  quality  control  program. Based on the customer requirement and market demand, the premix producer need to decide on the type of premix and its concentration to provide a safe, reliable and homogenous premix.

Premix Homogeneity

Homogeneity means that all ingredients in the premix are present in the same ratio they were added, throughout the product. There are various factors to be considered for producing a homogenous premix. The ones of importance are,

  1. Density of raw materials
  2. Particle size
  3. Particle surface
  4. Electrostatic charge of particles
  5. Hygroscopicity
  6. Compatibility
  7. Type of carrier/diluent used
  8. Mixing time
  9. Mixing order
  10. Degree of filling of mixer


It is the amount of mass that can be accommodated in a specific volume. The various raw materials in a premix can be of varying density from low, medium to high density and they should be taken care of to be produce a mix of optimal density, to achieve uniform mix. If not handled effectively, the premix coming out of the mixer can very well seem to be an efficient one, but might turn out to be a non-uniform premix during transit.

Particle size:

Fine particles contribute to better homogeneity than a coarse one, but pose handling issues, which needs to be addressed in a proper way.

Particle surface:

The surface of particles can be smooth or rough. Rough ones contribute to more homogeneity than the counterpart does.

Electrostatic charge:

All the particles carry charge on their surface. Smaller the particle size more will be the charge carried by the particle; and more will be the negative impact on homogeneity.


This is the water absorbing capacity of the raw material. More the capacity, bad will be its effect on uniformity.


A good knowledge on the interaction of raw materials is a must that further enables homogenous premix production.

Type of carrier/diluent used:

Carrier is an inert material that is compatible with other raw materials. Selection of carrier and its percentage is important for formulating a quality homogenous premix. It is generally preferable to leave sufficient space for a carrier in order to achieve a homogenous mix.

Mixing time:

This should be an optimal one and both less and more time would lead to improper mixing and de-mixing respectively affecting the homogeneity of produced premix. The first optimal mixing time can only be determined on the basis of homogeneity (CV) tests.

Mixing order:

Particles of varying density and size need to be added in appropriate order onto the mixer to get a homogenous mix.

Degree of filling of mixer:

Both under and over filling of mixer might lead to non-uniformity in premix.

Measures of homogeneity:

A basic requirement to homogeneity checking is to dispose over an appropriate analytical method for the examination of the composition of the samples. Often-indirect methods are applied for measuring homogeneity like, mixing lightly dissoluble dye to the other components, then dissolving the dye from the samples and determining it spectrophotometrically. Other materials can also be applied instead of dye, e.g. colloidal iron metal was used by American researchers and iron oxide by Czechoslovakian researchers for homogeneity examinations of feeds. These methods are, however, not ideal solutions at all, and give only approximate information regarding the homogeneity of the other components of the mixture. The individual physical characteristics of these particles usually differ from those of the other components, and thus their mixing characteristics are different as well. This would interfere with the measurement of homogeneity, more so with uniform premixes.

Methods for homogeneity examination of premixes are more reliable when the distribution of some actual components of the premix is examined. These processes dealing directly with the actual components of mixtures, provide more information about the system than do the
in-direct ones, although in this case too, the homogeneity to be similar to that of the other components of the mixture can only be supposed.

Co-efficient of variation (CV) studies:

Samples of 10 or more need to be collected from various parts of the mixer or from different bags of the same batch produced. These samples would then be tested for a specific component of premix. CV is then calculated for those analysed values, which should not deviate more than ± 5% of the claimed value.

Effects of homogenous premix:

When the components of premix are uniformly distributed throughout a premix, it ensures that, that specific nutrient is equally available to the animal from any part of premix. This enables a consistent and repeatable flock/herd performance. The entire process of premix production and the resources spent in making that premix, will go vain, if homogeneity is not achieved. In such a case, it would not be a justice to label that mix as a premix. A non-uniform premix should never be fed to animals, as there is always associated risk of under-dosing or over-dosing of certain nutrients to the animals, leading to non-uniformity and sub-optimal performances in flock/herd.


Premix production technology is not the same as that of complete feed production. A quality premix can be manufactured only through a stringent quality control & assurance program and good manufacturing practices. In order to obtain this objective, it is of great importance to establish an appropriate technological process, approximate characteristics of raw materials and choice of the appropriate formula. Equable distribution of particles must be sustained during the whole process of preparation as well as afterwards, during bagging and further transportation to end consumers. The process of homogenization in premix production is ensured by measuring the active ingredients in premix samples. Homogeneity of premix is a critical and crucial factor that determines the quality of premix and its capability in providing the right nutrients to the animal as per their requirement that finally translates into efficient productivity and profitability.