The Feed Hygiene directive, EC No. 183/2005, twice mentions the notion of cross-contamination in the parts devoted to feed manufacturer’s facilities and production. It stresses the notions of facility design: “The lay-out, design, construction and size of the facilities and equipment shall be such as to minimize the risk of error and to avoid contamination, cross-contamination and any adverse effects generally on the safety (sic)” and control of manufacturing practices: “Technical or organizational measures must be taken to avoid or minimize, as necessary, any cross-contamination and errors”.

There is no official definition of cross-contamination. Nonetheless, it is generally accepted that this notion refers to the transfer of an additive or drug from one feed where it is accepted to another feed where it is not accepted.
This notion is usually easily grasped when it concerns production batch remnants that remain in the system and are then picked up by subsequent batches. Yet it also refers to other more complex transfers.
At Tecaliman, the cross-contamination works began with the application of the directive 95/69. After evaluating the risks relating to practices and facilities at industrial sites, it rapidly became clear that the profession needed a common method to evaluate cross-contamination generated by remnants left in circuits and transferred to successive batches.
The French government and the industry validated and accepted this method as the reference in the matter, regardless of the type of tracer used. At the same time, Tecaliman developed an analysis technique using an external tracer (RF blue lake micro-tracer). This system detects extremely low contamination (0.2%) by following a protocol that reduces test costs while providing a good diagnosis of the contamination sources in any industrial process. This methodology and the analysis technique are used daily in most French companies today.

The use of a common reference method allowed us to compare performance between sites and generally helped French industry reduce its cross-contamination level by almost 50% from 2000 to 2003. Today, over 50% of French companies have less than 3% cross-contamination in the first collector batch and less than 1% in the second.
There are three underlying reasons for cross-contamination of subsequent batches.
Firstly, transfer of a consistent amount from one batch to the next in the form of remnants left at the bottom of the circuit.
Secondly, dust particles containing a higher additive concentration left in the circuit between two batches, suspended in the air or stuck to the circuits’ overhead structures.
Lastly, dust particles with high additive content captured by the filtration systems that are re-deposited at the end of the batch.

The best way to prevent cross-contamination is undoubtedly to shorten the circuit between the point where hazardous additives are introduced and the granulation point or final packing point. It is impossible to achieve zero cross-contamination due to the ordinary physical behaviour of pulverulent environments in complex animal feed circuits. We can only hope to minimize it through controls.