Although reports of violative residues in meat and poultry are uncommon, such residues are found in certain classes of animals such as market (formerly, "cull") beef and dairy cows more frequently than in other classes. Several initiatives portend greater attention to violative residues.
The USDA Food Safety and Inspection Service continually revises the National Residue Program to enhance its risk-based public health focus. Last year the FSIS instructed its field veterinarians to test for residues in cattle that have postmortem signs of illness or disease, a change that could lead to an increase in the number of identified residue violations. When this type of approach was adopted by a veterinarian at a plant in Pennsylvania, the number of residue violations in that plant rose dramatically. Now the FSIS is collecting data from market cow slaughter operations across the country to ensure that the agency's residue control program is being implemented correctly and uniformly.
The FSIS is making additional changes in the National Residue Program. The agency has imposed on packers new regulatory requirements that a hazard analysis be performed by the slaughter establishment. The establishment should consider the necessity for including measures for avoidance and/or detection of residues as part of the plant's Hazard Analysis and Critical Control Point program. The plant may test for residues or may ensure that it purchases animals only from reliable suppliers.
Also, regulatory changes are expected that will mandate condemnation of the entire carcass based on the finding of violative residues in the target tissue, as defined by the FDA. Coupled with the new sample selection procedure, the packing industry is expecting a substantial increase in the number of carcasses being condemned.
Industry groups are responding with a proactive strategy to keep violative residues out of the human food supply. Possibly included in the strategy is development of a public list of animal consignors who have been investigated and determined by the FDA to be a "responsible party" for the presence of an illegal drug residue.
Of particular concern are results from a recent testing of samples from cow slaughtering plants for nonsteriodal anti-inflammatory drugs such as phenylbutazone and flunixin meglumine. Earlier this year, the FSIS conducted some initial studies to determine the applicability of a new rapid screen for these drugs but then suspended the new test until the project can be expanded to cover market cow plants across the country. The agency is concerned by the public health implications of high numbers of animals with violative levels of these compounds.
The National Milk Producers Federation announced specific recommendations regarding these two drugs. When member producers are working out treatment plans with their veterinarian, the federation urges them to generally avoid use of phenylbutazone and to use flunixin meglumine carefully.
In the absence of an approved, effective drug labeled for a necessary indication, veterinarians may contemplate extralabel drug use. When treating food animals with drugs in an extralabel fashion, veterinarians must preferentially use an effective drug bearing a food animal label over a human or companion animal drug. High drug cost is not an acceptable medical rationale. Extralabel drug use is not permitted if it would result in a violative food residue or any residue that may present a risk to public health. Practitioners should refrain from administering, dispensing, or prescribing a drug in an extralabel manner if they have concerns about a producer adhering to an extended withdrawal time.
Because flunixin meglumine is approved for use in cattle, the Food Animal Residue Avoidance Databank counsels practitioners that flunixin meglumine is the "NSAID of choice." FARAD strongly discourages the use of phenylbutazone in any food animal species, citing food safety data and legal requirements of extralabel drug use.
Because phenylbutazone can be detected in the urine of treated animals for extended periods after treatment, FARAD estimates the slaughter withdrawal time for IV, extralabel phenylbutazone administration in cattle (up to 4.4 mg/kg) to be 45 days and the milk withholding time to be 120 hours.
In contrast, the slaughter withdrawal time for labeled IV use of flunixin meglumine in beef cattle is four days. FARAD recommends using the label slaughter withdrawal time of four days for lactating dairy cattle, and estimates the milk withholding interval following extralabel, IV administration of flunixin meglumine to be 72 hours.
The regulations of the Animal Medicinal Drug Use Clarification Act describe all the requirements of a veterinarian who finds it medically necessary to use a drug in an extralabel manner. A summary brochure titled "Extralabel Drug Use " and an FDA publication titled "FDA and the Veterinarian" are available free of charge from the AVMA.
Dr. Lyle P. Vogel, director of the AVMA Scientific Activities Division, and Dr. Elizabeth Curry-Galvin, assistant director