Detection of antibiotic and sulfonamide residues in bob veal calf tissues: 967 cases (1987-1988)

The data on antimicrobials in bob veal calves obtained by USDA-Food Safety Inspection Service (FSIS) during the fiscal year 1988 were reviewed. Of 3,095 calf antibiotic and sulfonamide test (CAST)-positive carcass submissions, 967 were chosen by FSIS for antimicrobial residue analyses. Specimens of muscle, liver, and kidney were obtained at abattoirs as a part of the FSIS program, and the results were reviewed by calf submission. At least 1 tissue from each of 425 submissions contained neomycin. Unidentified microbial inhibitors were found in 291 submissions. Streptomycin was found in 86 carcass submissions, penicillin in 81, sulfamethazine in 73, tetracycline HCl in 59, and gentamicin in 53. Other monitored agents were found in less than 50 submissions each. Only 257 submissions included evaluation for sulfonamides, but sulfamethazine was found in 28.4% of them. Chloramphenicol was not detected. Concentrations of neomycin in kidney specimens ranged from 0.25 to greater than 100 ppm, and differed among the 3 regional laboratories (West, Midwest, and East). The western region had the greatest proportion of low-concentration specimens, whereas the midwestern laboratory had the largest proportion of specimens with very high concentrations (greater than or equal to 100 ppm) of neomycin in kidney tissue. Data to identify the sources and causes of the residues were not available. However, the western laboratory evaluated CAST-positive submissions from calves certified to be antimicrobial-free, whereas the other laboratories evaluated submissions from certified and noncertified calves; therefore, this may partially explain regional patterns for neomycin quantities in kidney specimens. Neomycin predominated among CAST-positive verifications. A high prevalence of unidentified microbial inhibitors suggests further identification may be warranted.