USDA’s Food Safety and Inspection Service has replaced the Fast Antimicrobial Screen Test with the Kidney Inhibition Swab test for swine carcasses at processing plants, with the completion date set for the end of 2012.  Carcasses for sampling and testing by the KIS test are selected in the same way as carcasses selected for FAST.

In addition, FSIS has updated the confirmation step used when a positive antibiotic sample surfaces. The new test is more specific and able to confirm residues of a particular antibiotic. “FSIS has switched its procedure from a biological test to a chemical test to confirm a positive screening test for antibiotic residues,” says Paul Sundberg, DVM, vice president, science and technology for the National Pork Board. “The new confirmation step increases the ability to arrive at a definitive answer on violative residues in meat.”

FSIS has had occasional instances of residues resulting from procaine penicillin injections in cull sows. “Even if withdrawal times are strictly observed, there are situations that may arise that would require an extended withdrawal period,” Sundberg says. NPB is currently conducting research to verify the potential for detecting penicillin residues.

It appears that the amount of penicillin administered into an injection site affects the potential of detecting residue violations in sows. The recommended withdrawal time for procaine penicillin is at least 15 days, according to Sundberg.  “Our research is investigating if this will be sufficient even for our domestic markets, given the likely uses of procaine penicillin on the farm and the sensitivity of the new tests.”

If a sow requires a penicillin injection, no more than 10 mL (10 cc) should be injected into one site. It is also important to select different injection sites if a sow requires more than one treatment, Sundberg says. The issue has not been reported in finished slaughter hogs.