Depletion of tylosin from the mammary gland of mastitic cows and its influence on the qualitative properties of milk

Six cows suffering from mastitis were injected intramuscularly with tylosin at a dose of 10 mg kg(-1) b.w. for five consecutive days after the morning milking. The milk samples were collected for 13 days at 12 h intervals, and from the afternoon and morning milkings were pooled together (1:1). The samples were analysed by liquid chromatography and yoghurt inhibitor test for a detection of tylosin residues. Qualitative parameters of milk (active acidity, somatic cell count, total bacterial count) were also investigated. It was found that the HPLC method and yoghurt inhibitor test gave comparable results. The somatic cell count was above 400 000 per mi of milk. Staphylococcus aureus and pathogenic streptococci were detected in milk from mastitic cows.