Poultry feed may contain added coccidiostats to eliminate the parasite, Eimeria.

Because the feed industry has not managed to prevent contamination caused by coccidiostats, the EU has set maximum limits for residues.

The use of coccidiostats is banned for laying hens. Coccidiostats are permitted in the feed of broilers, pullets and turkeys within the restrictions set in the approval decrees, concerning minimum and maximum concentrations and the withholding period.

The purpose of the regulations is to eliminate coccidiostat residues in foods derived from poultry.

Despite the restrictions, coccidiostat residues have been found in both eggs and poultry meat.

One of the causes is contamination of feed during preparation.

Coccidiostats are dust-like and electrically charged, so they can remain on the feed preparation conveyor in spite of careful cleaning.

The research study conducted showed that even very low coccidiostat concentrations in feed caused discernible residues.

The study developed a liquid chromatography–mass spectrometry (LC-MS) method capable of detecting coccidiostats at the maximum concentration levels set by the EU. The study also investigated how quickly coccidiostats disappear from the feed preparation mixing and granulation line when feed containing coccidiostats was followed by feeds not containing them.