Antibiotic Residues in Milk Supplies in Zimbabwe.

Raw milk samples from 73 individual milk producers were obtained at the three main Dairy Marketing Board (DMB) collection centers in Zimbabwe during the period of January to February, 1988. The samples were examined for the presence of antibiotics using the Delvotest-P (Gist-Brocades) ampoule test method with a sensitivity of 0.002 I.U. of penicillin per ml of milk. Four samples (5.5%) contained more than 0.005 I.U. of penicillin per ml or equivalent. Two (2.8%) samples contained antibiotics other than penicillin. An antibiotic depletion study using 23 cows treated with a multiple antibiotic intramammary infusion product, streptomycin - penicillin mixture (Dispolac RX4 B®; Coopers, South Africa), indicated a withholding period of 7-8 d was necessary to obtain milk free of detectable residues. The sensitivity of the Delvotest-P for streptomycin was determined by the manufacturers and found to be 4-6 μg/ml.