Dr. Moses Kyule, Dr. Kelay BelihuDr. Girma Zewda, Dr. Tadelle DessieDESALEGNE, ABEBEW2020-06-172023-11-082020-06-172023-11-082008-06http://etd.aau.edu.et/handle/123456789/21659A cross-sectional study was conducted between October 2007 and May 2008 to detect and determine oxytetracycline and penicillin G residue levels in bulk milk of cows in Debre Zeit and Nazareth dairy farms. A total of 400 bulk milk samples were randomly collected from the respective study dairy farms. A questionnaire survey was carried out by personal interviews with dairy farm owners in Delvotest positive farms (cases) and Delvotest negative farms (controls) to identify various risk factors and to determine associations among the occurrence of antibiotic residues in milk. All samples were qualitatively screened for antibiotic residues by Delvotest SP assay. Concentration of the positive samples was determined by high performance liquid chromatography. Concentration was established using linear calibration reference curves. Out of 400 samples analyzed for antibiotic residues, 46 (11.50%) had detectable antibiotic residues. In Debre Zeit dairy farms, 34 (12.19%) and in Nazareth, 12 (9.92%) milk samples were positive for antibiotic residues. The mean residue level of oxytetracycline was 142.00μg/l and 125.25μg/l in Debre Zeit and Nazareth dairy farms and that of penicillin G was 4.77μg/l and 4.52μg/l in the two dairy farms, respectively. Oxytetracycline concentratyions in all samples in Debre Zeit and Nazareth dairy farms ranged at a concentration between 27-251μg/l and 45-192 μg/l, respectively. The antibiotic residues positive samples which showed residue of oxytetracycline above the WTO/FAO/CAC established maximum residue limit of 100gμ/l were 24 (70.58%) and 10 (83.33%) in Debre Zeit and in Nazareth dairy farms, respectively. For penicillin G with maximum residue limit of 4μg/l, they were 7 (20.58%) and 2 (16.66%) in Debre Zeit and Nazareth dairy farms, respectively. Penicillin G was found in some milk samples in Debre Zeit 19(58.8%) and Nazareth 5(41.7%) dairy farms. The results obtained confirmed that oxytetracycline and penicillin G were imprudently used in dairy farms. Results of the present study serve as preliminary base-line information for veterinary authorities, drug administration and quality control, other concerned organizations and professionals to take necessary measures in controlling and preventing of occurrence of drug residues in milk and other food products.enDebre ZeitDelvotest SPHigh performance liquid chromatographyMilkNazarethOxytetracyclneThesis