Investigation of the persistence of florfenicol residues in bovine milk and fate during processing

The persistence of florfenicol residues in milk and their migration to dairy products was investigated following treatment of six lactating dairy cows with Selectan 300 mg mL−1 solution for injection at a dose of 1 mL 15 kg body weight−1. Florfenicol residues were measurable (LOQ 1.0 μg kg−1) in the milk of three cows for up to 27 days post-treatment but were not detectable at day 34. On day 3 post-treatment, the milk was pooled into two independent aliquots, each containing the milk from three cows. One part of each aliquot was pasteurised. Milk products were manufactured from the pasteurised and unpasteurised aliquots. The florfenicol residue concentration in cheese was similar to the initial milk (989 versus 845 μg kg−1, respectively). Residues in skim-milk powder were approximately eight-fold higher than the skim milk used for its manufacture (8927 versus 1089 μg kg−1, respectively).