2.47 Feedmills have been aware for decades of the risk of cross-contamination between batches of feed intended for different species. Similarly a blended batch of feed will leave microscopic traces which will be picked up by the next batch in the system. If a batch of dairy compound follows a batch of pig compound, microscopic traces of the raw materials in the pig compound could be found in the dairy compound. Prior to BSE this low level contamination was considered a problem only when drugs were being incorporated. Macro as well as micro levels of contamination can take place in feedmills.
Raw materials can adhere to the sides of bins and conveyers and build up sizeable agglomerations.
In time these agglomerations can fall into the stream of material and may corrupt a formulation. Formulators can make mistakes. The software in a feed mill which controls weighing and blending can be corrupted for various reasons. At the point of intake a material can be consigned to the wrong bin resulting in an unplanned mixture of raw materials. Raw materials which were themselves semi-products containing a number of component raw materials were on sale to compounders and were bought because they appeared to be cheap sources of nutrients.