Survey of chloramphenicol residues in diseased swine

Tissue samples from 279 hogs suspected of having received antibiotic treatment were collected at federally-inspected abattoirs and submitted for chloramphenicol residue analysis during August and September 1984. Injection sites (when present), kidneys or muscle samples were tested by one of two gas chromatographic methods. Kidney samples were also tested at the abattoirs by the Swab Test On Premises. Thirty-one animals (11%) were found with detectable levels ranging from 1 part per billion to 5727 ppb. Highest levels were found at the injection sites, while levels in muscle tissue did not exceed 500 ppb. None of the kidneys from animals found to contain chloramphenicol residues produced a positive Swab Test On Premises result attributable to the presence of chloramphenicol. Twelve kidneys from animals free of chloramphenicol residues produced positive Swab Test On Premises results. Of these, five contained penicillin or streptomycin, but antibiotic residues were not detected in the remaining seven. In addition to the samples collected for this survey, samples from eight hogs representing a herd which had been treated for pneumonia were submitted by an abattoir in Manitoba in November 1984. Chloramphenicol levels in these animals ranged from 0.1 to 73 parts per million in the injection sites, and from 0.04 to 21 ppm in the muscle tissues. The survey data indicated that there were a significant number of animals reaching the abattoirs with detectable chloramphenicol residues, and that the Swab Test On Premises procedure was ineffective in detecting these animals.