GMP+ for the Production of Feed Materials, Compound Feed and Additives — a Complete Guide

Below we describe exactly what sets production certification apart from the general GMP+ requirements shared by every participant in the system — control of the manufacturing process itself, mixture homogeneity, prevention of cross-contamination, the specifics of producing feed additives, and the storage and labelling of finished products.

Who this certification scope applies to

The GMP+ production scope covers companies manufacturing feed materials (e.g. meals, bran and other processed raw materials), compound feed (complete or complementary, for farm animals or pets) and feed additives and premixes — substances or preparations added to feed in relatively small quantities to achieve a specific nutritional, technological or zootechnical effect. In practice this covers both large industrial feed mills and smaller plants, including farms producing compound feed for their own use on a larger scale or for sale, as well as specialised plants manufacturing premixes and feed additives for other compound feed producers.

A company may hold certification covering a single type of production or several at once — for example, a plant manufacturing both feed materials and finished compound feed. The certification scope should precisely reflect the actual production profile, since it determines which detailed requirements (and which risks) the auditor will assess during the site visit.

Production certification also covers farms carrying out so-called own-use production on a scale exceeding typical farm consumption, as well as plants manufacturing pet food on behalf of other companies (contract production). In each of these cases the principles governing process control and cross-contamination prevention are the same — only the scale of the required documentation differs, adjusted to the actual size and complexity of the production.

General requirements as the foundation of production certification

Before discussing the elements specific to production, it is worth stressing that all the general GMP+ requirements — a documented quality management system, HACCP analysis, traceability, contaminant monitoring, supplier management and incident procedures — apply to a production plant in full, exactly as they do to any other participant in the GMP+ system. The elements described in the rest of this article do not replace those requirements; they supplement them with issues typical of the manufacturing process itself. A full description of the general requirements is available on the GMP+ Standard Requirements page.

Control of the production process

Beyond the general quality management system requirements, a production plant must document control of the key stages of the manufacturing process: receipt and inspection of incoming raw materials, dosing of ingredients according to the recipe, mixing, any pelleting or other technological processing, and finally, inspection of the finished product before it leaves the plant. For each of these stages, the company should specify which parameters are controlled (e.g. raw material moisture, weighing accuracy, mixing time), how often, and who is responsible.

Another important element is control of the dosing and weighing equipment — its periodic calibration and documented accuracy checks. Dosing errors, particularly for highly active ingredients (e.g. feed additives used in small quantities), can lead both to a shortfall in the intended effect and to safe levels of a given substance being exceeded in the finished product.

Inspection of incoming raw materials should cover not only verifying compliance with the order (type, quantity, delivery documentation) but also assessing the physical condition of the delivered material — smell, moisture, the presence of visible contamination or signs of pests. A record of this check, even in a simple form (e.g. ticking off points on a checklist at receipt), provides basic evidence that the raw material entered production only after verification, rather than automatically upon unloading.

Mixture homogeneity and validation of the mixing process

One of the key technical requirements for compound feed producers is ensuring adequate uniformity (homogeneity) of the mixed ingredients — so that samples taken from different points in the same batch have a similar composition. This is achieved through an appropriate choice of mixing time and method, matched to the specific mixer and the type of ingredients being mixed (differences in density, particle size or the electrostatic properties of raw materials can make achieving homogeneity more difficult). The more ingredients with varied physical properties a recipe contains, the harder it is to achieve even mixing in a short time — something worth taking into account already at the recipe-design stage.

The standard expects the company to carry out and document validation of the mixing process — a practical test confirming that, at a given mixing time and method, the mixer actually achieves the required homogeneity. Validation is repeated periodically and after significant changes — equipment upgrades, a recipe change involving ingredients with different physical characteristics, or noticeable deviations in the quality control results of finished mixes.

In practice, validation is carried out by taking several samples from different points in the mixer (e.g. the top, middle and bottom of the chamber) after a standard mixing cycle, and comparing the analysis results for one marker present in the recipe (e.g. a trace element in a small, easily measurable quantity). If the results from the individual points fall within a narrow, pre-defined deviation range, the mixer is considered validated for that mixing time. Too short a mixing time is one of the most common causes of non-homogeneity — under production-output pressure, plants sometimes shorten the mixing cycle below the value confirmed by validation, which directly lowers the quality of the finished product.

Preventing cross-contamination and the production sequence

Plants that manufacture different recipes on a shared production line — including some containing sensitive ingredients such as coccidiostats or other additives with restrictions on target animal species — must manage the risk of cross-contamination from residues of the previous batch. In practice, companies apply a planned production sequence: manufacturing products without sensitive additives before products that contain them, using flushing (transition) batches between recipes with different risk profiles, or full line washing where sequencing alone is not sufficient.

The effectiveness of the approach adopted — sequencing, flushing batches or washing — should be verified in practice, for example through periodic testing of residue levels in the first batch manufactured after a line changeover. A procedure description in the documentation alone, without such verification, gives no assurance that the measures adopted actually limit the risk to an acceptable level — and this is exactly the kind of evidence auditors like to check during a site visit.

Planning the production sequence requires a good understanding of the full portfolio of recipes being manufactured — it is not enough to set a general rule once, such as "products without additives first, then products with additives." As the product range expands, the company should periodically verify whether the adopted production order still reflects the current risk profile of all recipes, not only those on offer when the procedure was first established. A new recipe introduced into production should undergo the same risk assessment as ingredients that have been in the system from the start.

The specifics of producing feed additives and premixes

Producers of feed additives and premixes usually operate in a higher-risk area — a small deviation in the dosing of a highly active substance has a proportionally greater impact on the safety of the finished product than a similar deviation in the production of a standard compound feed. For this reason, the requirements for dosing precision, quality control of incoming raw materials, and line washing and cleanliness checks are typically more stringent here, and the scope of finished-product quality testing is broader.

Companies in this segment often also implement the FAMI-QS standard, which focuses precisely on the specifics of producing feed additives and premixes — in many areas it complements GMP+, which allows some shared documentation to be used when implementing both standards in parallel. More information is available on the FAMI-QS page.

Premix producers should also pay particular attention to the quality control of carriers — inert substances on which the active ingredients of the additive are distributed. The physical properties of the carrier (particle size, density, binding capacity) directly affect the homogeneity of the finished premix, and changing carrier supplier — even while keeping the same nominal specification — may require re-validating the mixing process.

Storage of raw materials and finished products at the plant

The production scope also covers storage carried out directly within the plant — both of raw materials awaiting processing and of finished products before dispatch to the customer. This requires proper separation of incompatible raw materials and products (e.g. with different status regarding the presence of allergens or sensitive substances), suitable storage conditions (temperature, humidity, pest protection) and clear batch marking enabling unambiguous identification. If a company carries out storage as a separate trading activity not directly linked to its own production, we describe that area separately on the GMP+ for Trade and Storage page.

Another important element of storage at a production plant is stock rotation — applying the "first in, first out" (FIFO) principle when drawing raw materials for production, so as to avoid batches being held for an excessive, uncontrolled length of time, which can affect raw material quality (e.g. moisture loss, mould growth under unfavourable conditions). The warehouse system — even a simple one based on batch numbering and receipt dates — should support this rotation rather than leaving it entirely to the warehouse worker's memory.

Labelling of finished products

Correct labelling of finished compound feed and additives is an important element of the producer's responsibility — both in the context of feed law and of GMP+ traceability requirements. The label should make it possible to unambiguously link the product to a specific production batch and should contain the information the recipient needs to use the product safely. Detailed requirements for feed labelling are described on the Feed Labelling page.

Quality control of the finished product before release

Before a batch leaves the plant, it should undergo a final check confirming compliance with the recipe and quality specification — covering both physical parameters (e.g. moisture, appearance, smell) and, depending on the risk profile, laboratory testing of selected chemical or microbiological parameters. The company sets the scope and frequency of this testing based on risk analysis, in the same way as for the general contaminant monitoring plan described on the GMP+ Standard Requirements page.

The result of the final check should be documented and clearly linked to the specific batch before it leaves the plant — a general statement such as "product checked" is not enough; what is needed is a specific record showing who carried out the check, when, and what the results were. If a deviation from specification is detected, the batch should be held pending investigation, in accordance with the documented non-conforming product procedure, before it is released for further distribution.

Managing recipes and production changes

Production recipes should be formally approved and version-controlled, so that at any time it is possible to state unambiguously which recipe version was used to produce a specific batch. A recipe change (e.g. replacing one raw material with another of similar parameters) should go through the change management process described generally in the standard's requirements — with an assessment of whether the change affects the previously conducted HACCP analysis, mixing validation or monitoring plan, before it is implemented in current production. This applies both to changes in raw material composition and to technological changes — for example, a different order of adding ingredients, or a change in the time and temperature of technological processing. Even a seemingly minor modification, introduced without a formal assessment, can in practice affect mixture homogeneity or the effectiveness of cross-contamination prevention.

In practice, well-organised plants maintain a simple recipe version register in which every change is dated, justified and linked to the person who approved it. This helps avoid a situation in which informally modified "working versions" of recipes circulate on the production floor, invisible in the official documentation — one of the more common sources of discrepancies found during an audit.

Maintenance and the technical condition of production equipment

The technical condition of production machinery — mixers, dosing equipment, internal transport systems (conveyors, elevators) — has a direct impact on the safety and quality of the feed produced. The standard expects a documented inspection and maintenance plan for key equipment, covering both routine activities (cleaning, lubrication, checking component wear) and the response to failures that could affect product quality, such as leaks leading to dust contamination or contact with metal parts.

Particular attention is worth paying to equipment in direct contact with the product, where damage (e.g. coating chips, cracks) can lead to physical contamination of the finished mix. A register of inspections and repairs for such equipment is a commonly checked element when the auditor assesses overall control of the production process.

Plant hygiene and pest control

A production plant should have a documented, regularly implemented hygiene programme covering a cleaning schedule for individual zones (production, storage, staff areas) and a pest control programme — both preventive (monitoring bait stations, checking entry points) and reactive, in case pests are detected. In feed plants, pest-related risk is particularly significant because plant-based raw materials are a natural food source for pests, and their presence can lead both to product losses and to microbiological or physical contamination.

Contract production and private-label feed production

Production plants increasingly manufacture feed on behalf of other companies — under the client's brand or for further resale. In such relationships, responsibility for compliance with GMP+ requirements remains with the actual producer (the plant carrying out the production), regardless of whose brand the product is sold under. It is worth ensuring that the agreement between the client and the production contractor clearly defines who is responsible for individual elements of the quality system — e.g. recipe approval, control of raw materials supplied by the client, or handling non-conformities — so that no gap in responsibility arises between the two parties in practice. A clear division of roles is especially important in the event of an incident — from the very start of the cooperation, both parties should know who initiates the non-conformity management procedure and who informs end customers about it.

Most common non-conformities in production plants

From audit experience in production plants, the most frequently recurring findings concern: a lack of documented mixing process validation, or validation that is out of date after an equipment upgrade; incomplete documentation of the production sequence when changing over the line between recipes with different risk profiles; a lack of periodic calibration of dosing and weighing equipment; and inconsistencies between the theoretical recipe and the actual production record (e.g. no documented reason for a deviation from the standard recipe in a specific batch). Deliberately preparing these areas before the certification audit significantly shortens the time needed to close out the certification process.

Less frequently mentioned, but still regularly recurring findings include: incomplete documentation of technical inspections for equipment in direct contact with the product, no clearly assigned responsibility for approving recipe changes, and inconsistency between the certification scope and the activity actually carried out — for example, contract production not formally included in the declared scope. Each of these areas is worth deliberately checking before the audit, ideally as part of an internal mock audit.

Where to start implementation at a production plant

A good starting point is to review the current production process for critical points specific to production — places where a dosing error or cross-contamination could occur — and to verify whether the existing washing and sequencing procedures are properly matched to the range actually being manufactured. The general course of implementation and certification, common to all scopes of activity, is described on the GMP+ Certification Process page.

In advisory practice, a good first step for a production plant is to draw up a process map — a simple diagram showing the successive stages of manufacturing, the points where cross-contamination or a dosing error could occur, and the places where some form of control is already carried out. Such a map, even sketched by hand during a meeting with the production team, makes it considerably easier to later complete the HACCP analysis and identify which elements of the system need refining first, before the company moves on to describing procedures in detail and compiling full documentation.

Glossary

Mixture homogeneity

The degree of uniformity in the distribution of individual ingredients within a mixed batch — a key quality parameter in compound feed production.

Mixing process validation

A documented test confirming that, at a given mixing time and method, a specific mixer achieves the required mixture homogeneity.

Coccidiostats

A group of feed additives used in the prevention of coccidiosis in poultry and other animals, requiring particular dosing control and cross-contamination prevention because of restrictions on target species.

Feed material

A raw material of plant, animal or mineral origin used directly in animal feeding or as an ingredient in the production of compound feed.

Feed additive

A substance or preparation added to feed in a small quantity to achieve a specific nutritional, technological or zootechnical effect, subject to separate legal regulations governing market authorisation.

Production sequence

The planned order in which successive batches are manufactured on a shared production line, set so as to limit the risk of cross-contamination between recipes.

Flushing batch

A batch of product deliberately manufactured between two recipes with different risk profiles, intended to capture and remove residues of the previous product from the production line.

Contract production

The manufacture of feed on behalf of another entity, often under its brand — responsibility for compliance with GMP+ requirements remains with the plant actually carrying out the production.