Premixing

A properly mixed feed should contain consistent amounts of each ingredient throughout the batch. A good mixing depends on many factors; including the mixer type, mixing time, particle size differences, binders, “pre-mixing” micronutrients, the order of ingredients added to the mixer, the nutrient profile of the mix, and the quality assurance program. This article will discuss the concept of “premix” and the importance of the premix process in quality feed production.

Let's go through an example. We have a 1 ton of feed batch containing 1 gram of a micro-component. We know that this micro-component is an active ingredient, critical to the final mix and animal performance. Now let’s assume that we add that micro-component directly to the batch. A quantity of 1 gram may become airborne before or during mixing. During mixing, it may become electrostatically charged and stick to the mixer. It can stay in the dead spots of the mixer.

Premixing of micro-ingredients in a suitable atmosphere is a common method used to ensure that these nutrients are evenly distributed in the final feed. This mixing must be done accurately and carefully under a strict quality control program. Vitamins, micro-minerals, antibiotics, mold inhibitors and flavorings are mainly added to feeds in the form of premixes. Addition rates ranging from 0,5 to 10 kg per ton of compound feed are common. These ratios depend on the mixing equipment and the type of feed produced. In Figure 1, a definition is made through the relationship between the concept of premix and other feed ingredients.

Figure 1 – Relationship of Premix Concept with Other Feed Ingredients

The premixing process also helps reduce animal and human exposure to potentially harmful compounds. Providing a safe and healthy product is one of the most important goals for any feed manufacturer.

Premix is also used to standardize the effects of fermentation products such as some antibiotics and vitamins. Thus, more efficient use is ensured in the feed production process.

In an effective premix process, each of the following should be considered:

• Premix formulation
• Selection of carriers and diluents
• Use of dust control and binding agents
• Type of mixer used
• Sequence of ingredients added to the mixer
• Mixing sequence and mixer clean-out
• Packaging material selection
• Labeling
• Date coding
• Storage

Let's explain these titles one by one.

Formulation

This first step is extremely critical and should be performed by a qualified nutritionist or technically trained person. This person may be responsible for determining the formula, or they might follow a ready-made formula; either way, this is a necessary first step. Most incorrect premixes are due to misinterpretations by formulators.

Appropriate conversions involving units of measure are often underestimated. The formulator should also consider the source of ingredients, bulk densities and particle size differences, cost comparisons, and possible interactions of ingredients before final decisions are made. The nutrient content and effects of vitamins and minerals may vary between sources. These factors should be taken into account when formulating high quality premixes.

Formulators should consider possible interactions when preparing the formulas. Much debate continues among nutritionists about the combination of vitamins and micro-minerals in the same premix. Vitamin manufacturers have made efforts to protect the potency of their products in various ways. Some of those are; the addition of stabilizing agents, the use of coatings, the use of water-soluble or water-dispersible forms.

Vitamin and micro-mineral combinations will no longer be a problem if wise decisions are made about packaging, storage times, storage conditions and using quality vitamin suppliers. Convenience, cost savings and mixing efficiency can be advantages of such premixes containing both vitamins and micro minerals.

Image – Premix Ingredients
 

Carriers and Diluents

The purpose of the carrier is to physically accommodate fine-powdered micro-components and provide a uniform distribution in the process. Rice hulls are widely used carriers in vitamin premixes due to its homogeneity, pore shape and degree of porosity which allows fine particle stabilization. Other common carriers include calcium carbonate, corn cob fractions, wheat midds and corn distillers dried grain + solubles.

Diluents are used to extend or dilute micro-ingredients. They affect the density of the mix and provide volume to the premix. One of the most common diluents used in premixes is calcium carbonate. Combinations of various carriers can also be used to achieve the desired bulk density and provide some cost advantages. Different carriers and diluents and their combinations vary depending on the purpose of the premix and its use in compound feed.

Low-priced premixes often use high levels of calcium carbonate and require a high level of use in compound feed. Nutritionally, although this is a lower priced premix, it can have a negative impact on the calcium to phosphorus ratio and therefore, performance. Cost should not be the driving force in deciding which carrier or diluent to use. Rather, consideration should be given to the ability of these products to transport micro-ingredients and to their compatibility with other ingredients in a premix.

Dust Control / Binding Agents

Fats and oils have a very important function in quality premixes. By acting as an adhesive on the surface, they increase the micro-ingredient holding capacity of the carriers. Such bindingagents reduce dusting and improve the integrity and homogeneity of the premix. It also reduces electrostatic charges and possible losses of micro-ingredients.

Mineral oil, vegetable oils and fats can be used in selected premixes. Criteria affecting the selection are; the purpose of use of the premix, carrier type, carrier amount and oil/fat cost. Mineral oil is the most widely used additive in dust control for concentrated premixes; other oils and fats are used in more diluted products. Although cost targets are often taken into account in the type and amount of agent used for dust control or binding, this may reduce the quality of the premix. Some oils can cause vitamins to be destroyed if not stabilized.

Applying oils to mixtures under pressure to form an atomized oil droplet is the preferred method of application. This will ensure a homogeneous application and a higher quality mixture.

Type of Mixer

Rotary drum or horizontal mixers are required for proper premixing. These types of mixers handle a wide range of bulk densities in a better way. They produce less friction and therefore less heat is generated in mineral mixtures.
They also provide a greater surface area exposure when adding liquid. Ease of loading, ease of application of liquids, mixing efficiency, ease of discharge, and clean-out requirements must all be considered. Missing one or more of these issues can lead to major problems. Premix production is not the same as compound feed production. The same equipment is not always suitable for both processes, especially when it comes to mixing homogeneity.

Sequence of Ingredients Added to the Mixer

When filling a mixer, adding various ingredients in the proper order can affect the quality of the final product. When the sequence is not done correctly, undesirable situations such as oil balls, chemical interactions and particle separation may occur. This issue is even more important in premixes.

Low quality premixes are costly for feed manufacturers. During the premix process, the following procedure should be considered:

• Charge the mixer with the carrier.
• Disperse theoil (binder) evenly onto the carrier (this preconditioning step will maximize the carrier's carrying capacity).
• The diluent can be added at any time during the process.
• Micro-ingredients should be added after the preconditioning step to minimize oil balls and dustiness.

Depending on the type and properties of the premix, the addition order may need to be changed.
 

Sequence of Mixes and Mixer Clean-out

The mixers cannot be completely emptied and therefore a possible transfer from one mix to another occurs. Mixers differ in their discharge efficiency and steps must be taken to minimize this carryover. Physical cleaning using air or brushes may be required between two mixing periods. In special cases, it may be necessary to flush the entire system with rice hulls between mixes to reduce contamination.

Adding the ingredients in the proper order is a practical way of minimizing the negative effects of carryover. Various drug components and compounds that are toxic to some species are prime examples where sequencing is key. After mixing such ingredients, mixtures designed for animals should not be processed in the same mixer for the next batch.

Each drug mix should have its own sequencing schedule. Premix manufacturers must strictly follow this schedule even after proper cleaning, as potentially dangerous ingredients are involved.

When choosing a premix supplier, this quality procedure to minimize carryover is essential. The facility should also be visited before the final decision is made.

Packaging Material Selection

Packaging material should be selected according to the type of premix used. Moisture can be quite detrimental to the stability of some vitamins and other compounds; therefore, the packaging material must have a vapor barrier. Some ingredients used in premixes are hygroscopic and require a vapor barrier. Storage length and type of handling may also require consideration of special precautions at the packaging stage. For example, premixes to be exported may require stronger/thicker packaging materials due to handling types and possible weather variations.

Labeling

Labeling is extremely important to ensure regulatory compliance as well as correct use. Labeling guidelines that helped standardize this area are currently in place in the feed industry. Make sure that all products have a label.

Date Coding

Date coding should be a uniform requirement in the industry. Clear and easily identifiable date coding is useful for product rotation, biopotency concerns and expiration dates. A comprehensive explanation of the date coding used by the premix supplier should be requested.

Storage

Easily obtained premix products should be purchased at least monthly. The most desirable condition in storage is a dry and cool environment. An effective insect and rodent control program should be considered in storage areas. Highpotency premixes are usually expensive products. Therefore, proper storage is extremely important to ensure quality.

Several studies with properly formulated and blended vitamin and trace mineral premixes have shown good stability up to 90 days in storage using accepted analytic assays. However, storing premixes for more than 30 days is advantageous only in a few cases. A balance needs to be made between savings on premix purchases and costs associated with storage and possible stability concerns.

Many premix customers find that testing the final product is their assurance of quality and value. This approach can often lead to confusion for manufacturers and customers. It is very difficult to judge the value and quality of a given premix sample because variations in assays can be so wide. In addition, the analysis costs are quite high. This issue of variations is a growing concern for regulatory agencies, as standard procedures may not always adequately account for the level of vitamins. For example, cross-linked vitamin A cannot be detected by standard assay procedures. When assays are required, one should be aware of analytical variations and take all possible precautions to minimize them. Some of those precautions may be; correct sampling, using a reliable laboratory, having a routine sampling program, proper rotation and storage of premixes.

Summary

Quality can be achieved by working with suppliers that adhere to the principles outlined in this article. Reputable premix manufacturers have a strict quality assurance program; these companies do not blend out the overages supplied by the basic vitamin and drug manufacturers to their mixtures and employ successful and highly qualified technical people who provide or assist with premix formulations.

In summary, the premix process is not a simple process, it is one of the most important parts of a quality feed production process. It allows small inclusion nutrients and ingredients to be distributed more uniformly and safely throughout the feed.