Detection and quantification of antibiotic residues in goat milk in Mahikeng Local Municipality

Abstract

Goat milk could be used to reduce malnutrition since it is highly nutritious, and many people in rural communities in South Africa rear small ruminants for survival. However, the risk of food contamination by antibiotic residues is one of the significant problems facing public health, and is a result of the irresponsible use of veterinary drugs. One hundred goat farmers were interviewed using a questionnaire, and raw milk samples from 266 goats were collected and analysed for the presence of antibiotic residues. Screening for amoxicillin, tetracycline, sulfamethazine, erythromycin, and streptomycin residues was done using the enzyme- linked immunosorbent assay (ELISA) while high-performance liquid chromatography (HPLC) was carried out for confirmation. The questionnaire shows that all (100%) of the participants acknowledged the use of antibiotics on their goats and 99% of them were aware of the possibility of antibiotic residues in milk. ELISA results for residues of erythromycin, sulfamethazine and amoxicillin exceeded the Codex Alimentarius maximum residue levels (MRLs) in 94.7%, 82.3%, and 35.3% of analysed samples, respectively. Tetracycline was present in all (100%) analysed milk samples, and streptomycin was detected in 18.7% of samples; however, these results were below the recommended MRLs. The HPLC method confirmed the presence of streptomycin and tetracycline residues in 90% and 40% of the samples analysed. However, the concentrations were below the accepted MRL standards. Approximately 76.6% of samples exceeded the established MRL for sulfamethazine and 10% for erythromycin. Amoxicillin was not detected by the HPLC method. The results obtained in this study indicate a high level of contamination of goat milk with antibiotic residues, which may harm the health of the consumers.