Antibiotic residues in milk as risk factors of food chain - experimental tylosin treatment in cows suffering from mastitis

Six cows suffering from mastitis were treated intramuscularly after the morning milking with tylosin at a dose of 10 mg/kg b/w. for five consecutive days. The milk samples were collected just before the experiment (0 h), and 300 h (13 days) at 12-h intervals from the evening and morning milking, Staphylococcus aureus and pathogenic streptococci were detected in milk from experimental animals suffering with mastitis, however, Staphylococcus aureus was predominantly detected in milk samples from cows suffering from chronic mastitis until the last day of the experiment. Residue study in dairy cows indicated that cows with chronic mastitis excreted tylosin for longer periods than did the cows with acute mastitis. The concentration of tylosin in milk of these cows was not above the maximum residue level.