The effect of storage at 4 degrees C on antibiotic residues in kidney and meat tissues of dairy cows.

A method is described for the quantitative assay of antibiotic residues in the body of slaughtered farm animals by means of 3 types of agar media and 3 test organisms. With the help of programmed calculation procedures, data from large-scale tests for antibiotic residues could be analyzed accurately and rapidly. The concentrations of penicillin G, ampicillin, amoxycillin, cloxacillin, cephapirin, cephacetrile, neomycin, kanamycin, and oxytetracycline in the kidney, and also of tylosin in meat from the diaphragm muscle of cattle treated parenterally with these antibiotics were measured periodically in samples kept at 4 degrees C for up to 7 days after slaughter. The concentrations of penicillin G, ampicillin, amoxycillin and the cephalosporins in the kidney decreased rapidly upon storage whereas the levels of the other antibiotics remained essentially unchanged. Antibiotic stability in the meat was considerably greater than in the kidney upon storage for 4 days, and neomycin meat tissue levels were not reduced during storage for up to 144 hours. Results are discussed in relation to the conduct of the official qualitative Sarcina lutea Kidney Test and the most desirable procedure for preparing meat samples for assay.