In a basic survey of more than a thousand pork kidney samples, almost no veterinary drug residues were found, and none at levels that even approached U.S. regulatory limits, according to a study just published by an Agricultural Research Service (ARS) scientist in Food Additives & Contaminants: Part A.

Research chemist Weilin Schelver with the ARS Animal Metabolism-Agricultural Chemicals Research Unit in Fargo, N.D., pointed out that his findings "signal that U.S. pork producers are using veterinary compounds properly and indicate that veterinary drug residues in pork are not posing a health concern to U.S. consumers."

According to ARS, Shelver and his co-researcher Amy McGarvey purchased a total of 1,040 pork kidneys from four grocery stores in the Midwest and tested for residues of five commonly used veterinary drugs and feed additives: flunixin, penicillin G, ractopamine, sulfamethazine and tetracycline.

Pork kidneys are commonly used as an indicator meat because they are readily accessible and tend to concentrate drug residues compared to more commonly consumed muscle meats, ARS pointed out.

Only six samples from the 1,040 tested (0.58%) were positive when screened for antibiotics, indicating that these samples potentially contained antibiotic residues, Shelver said.

As a further check, a 278-sample subset of the pork kidney samples was screened with a more specific type of test for residues of four veterinary drugs: flunixin, a non-steroidal anti-inflammatory agent; ractopamine, an agent that enhances leanness in meat, and the antibiotics sulfamethazine and tetracycline. This testing used enzyme-linked immunosorbent assays (ELISAs), which, at times, are capable of measuring residues at far lower concentrations than those called for by regulatory tolerances.

Regardless of the testing method, residue levels of all veterinary compounds were always well below U.S. regulatory tolerances, ARS reported. For example, of the samples assessed by the highly sensitive ELISA and other methods, only 4% were positive for minute amounts of sulfamethazine, 10% for trace quantities of tetracycline and 22% for detectable quantities of ractopamine.

“The new report from the Agricultural Research Service reflects just how well U.S. pig farmers are doing with antibiotic stewardship in their daily goal of raising a very safe product for consumers to enjoy,” said Steve Larsen, a meat scientist who serves as the National Pork Board’s assistant vice president of science and technology. “It’s always good to get this kind of positive report card on pork safety, but we know producers and their veterinarians are never satisfied with the status quo and are always seeking new ways to do what’s right for people, pigs and the planet. This is reflected best in the National Pork Board’s "Position on Antibiotic Use in Pork Production," which emphasizes farmers’ dedication to raising healthy animals to help ensure a safe food supply.”

In addition, Larsen reiterated the role of the National Pork Board’s Pork Quality Assurance Plus certification program in helping farmers follow the appropriate withdrawal times for all Food & Drug Administration-approved antibiotics.

The board issued the policy position in September 2018 and noted that, through its pork checkoff, the board "supports objective, scientifically rigorous studies and risk assessments to help farmers make informed decisions regarding use of antibiotics in food animals and to build upon efforts to continuously improve antibiotic use best practices. The board also supports veterinarian oversight and best practices, as outlined in the long-established Pork Quality Assurance Plus certification program, which promotes education as an essential component of antibiotic stewardship and strongly encourages compliance with all regulatory requirements."