Liquid chromatographic determination of tylosin in mastitic cow's milk following therapy.

Liquid chromatographic analysis of milk samples from 6 cows treated with tylosin in a veterinary practice indicated that tylosin persisted in milk for more than 3 days after the final treatment. The concentration of tylosin was not below the stated maximum residue limit (0.05 mg/kg). The milk from 3 cows being treated for mastitis catarrhalis chronica contained tylosin residues for 3.5 days after the last withdrawal time (72 h). No residue was detected in the milk of any animal 6 days after cessation of therapy.