Examining the occurrence of residues of flunixin meglumine in cull dairy cows by use of the flunixin cull cow survey.

OBJECTIVE: To determine whether cull dairy cows with signs of certain clinical conditions, termed suspect, are more likely than healthy-appearing cull dairy cows to have violative concentrations of flunixin meglumine in their tissues at slaughter. DESIGN: Cross-sectional study. ANIMALS: 961 cull dairy cows. PROCEDURES: Suspect cull dairy cows were selected from 21 beef slaughter establishments with a high production volume of dairy cows, and kidney and liver tissues were collected for screening. Kidney tissues were screened for antibiotics and sulfonamides with the fast antimicrobial screening test (FAST). Liver tissues were screened for flunixin meglumine with an ELISA, and quantitative analysis of ELISA-positive samples was performed with high-performance liquid chromatography. During the same time period, liver tissues from 251 healthy-appearing cull dairy cows were collected for the Food Safety and Inspection Service National Residue Program Scheduled Sampling Plan, but were screened only for flunixin meglumine. RESULTS: Of 710 suspect cull dairy cows, 50 (7.04%) had liver tissue flunixin concentrations higher than the flunixin tolerance concentration (0.125 ppm). Thirty-one of 168 (18.45%) FAST-positive and 19 of 542 (3.51%) FAST-negative suspect cull dairy cows had violative tissue flunixin concentrations. Two of the 251 (0.80%) healthy-appearing cull dairy cows had violative tissue flunixin concentrations. CONCLUSIONS AND CLINICAL RELEVANCE: Suspect cull dairy cows, especially those that were also FAST positive, had a significantly higher incidence of violative tissue flunixin concentrations than healthy-appearing cull dairy cows at slaughter. Targeted sampling plans for flunixin meglumine in suspect dairy cows can help to support more efficient use of resources and further safeguard the nation's food supply.

Comparison of screening methods for antibiotics in beef kidney juice and serum.

Rapid screening tests can be used as part of an efficient program designed to monitor veterinary drug residues in cattle. In this work, three rapid tests designed to screen samples for the presence of antibiotic residues, the Fast Antimicrobial Screen Test (FAST), Premi and Kidney Inhibition Swab (KIS) tests, were compared using beef kidney juice and serum samples. In order to provide a realistic assessment, potentially incurred samples of beef kidney juice and serum were obtained from 235 carcasses which had been retained by inspectors in a processing plant for further testing. In addition, liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis was conducted on these samples to identify what antibiotics were present, if any, and their levels. The comparison of the three rapid screening test results with those from LC-MS/MS analysis allowed for a more complete comparison of the relative sensitivity of these analytical methods, as well as valuable information on false positive and negative response rates.