Prevalence of Antibiotic Residues and Associated Risk Factors in Milk in Chittagong, Bangladesh

We conducted the study to determine the prevalence and concentration of antibiotic residues (AR) in raw and pasteurized milk along with the effect of boiling on the concentrations as well as the associated risk factors on residues in raw milk. We collected 380 raw milk samples from commercial dairy farms, household farms and different distributing points, and 100 pasteurized milk samples from different markets of Chittagong, Bangladesh. A pretested questionnaire was applied to identify farm-level risk factors for AR followed by a univariate analysis to test the factors. The milk samples were screened for the presence of AR by Thin Layer Chromatography (TLC) and the concentration of residues (µg/l) was determined by Ultra High Performance Liquid Chromatography (UHPLC). Categories of farms, cow illness, treatment given in last week and antibiotics used in treatment were significant (P ≤ 0.05) factors for prevalence of AR in raw milk (18 %). The concentrations of amoxicillin (339.9 µg/l) and oxytetracycline (195 µg/l) residues in raw milk were significantly (P ≤ 0.01) reduced by boiling. The concentrations of amoxicillin and oxytetracycline residues in all sources of milk were higher than the Maximum Residue Limit (MRL) and assumed to be causing a serious public health threat.