Submitted to: Food and Agricultural Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 5, 2002
Publication Date: June 1, 2002
Interpretive Summary: Halofuginone (Hal) is a feed additive used to control parasites (coccidia) on the skin of broiler chickens. It is placed in the feed at a level of 3 parts-per-million. The chickens must be taken off the Hal treated feed at least 4-days before they can be used for food. Broiler chickens may be evaluated for levels of Hal in their liver tissue as a regulatory measure by the Food Safety and Inspection Service (FSIS). The current method used by FSIS for determining the level of Hal in chicken liver tissue utilizes a time consuming and complicated extraction procedure followed by high- performance liquid chromatography (HPLC) analysis. That procedure will not allow high sample throughput. We compared the results of analyzing for Hal by FSIS's HPLC analysis to the Agricultural Research Service's antibody-based immunoassay. Antibodies are substances that are produced by the immune system in response to foreign substances that enter the body. Once the antibodies are isolated they can be used to detect the foreign substances against which they were generated. The results of the two methods compare favorably. In most cases the recovery was higher using the immunoassay method. In addition, the immunoassay method does not require the use of chemicals that could be harmful to the environment, and that require proper disposal. The results clearly demonstrate that the immunoassay method could be used as a screening method (a way to look for Hal in large numbers of samples) in the regulatory arena for the analysis of Hal in chicken liver tissue.
Technical Abstract: Halofuginone (Hal) is a feed additive used worldwide to prevent coccidiosis in commercial poultry production. The current regulatory method for determining the action level of Hal residues in poultry involves measuring parent Hal in liver tissue by high performance liquid chromatography (HPLC). A competitive enzyme-linked immunosorbent assay (cELISA) for Hal was evaluated with respect to HPLC in determining Hal in 473 samples of chicken liver tissue obtained from commercial poultry slaughterhouses. Chicken liver samples were divided, and then analyzed by both the U.S. Department of Agriculture, Food Safety and Inspection Service's (FSIS's) regulatory method, and by the U.S. Department of Agriculture, Agricultural Research Service's (ARS's) cELISA method described here. The lower level of detection for Hal was 50 ppb by the FSIS HPLC method and 38 ppb by the ARS cELISA method. The lower cutoff limit for this study was 50 ppb as mandated by FSIS standard operating procedures. There was good agreement in the results obtained by HPLC and cELISA. In addition, the cELISA method does not require the use of organic solvents. These data clearly demonstrate that the cELISA method could be used as a screening method for the analysis of Hal in chicken liver tissue. If the cELISA had been used as a screening tool in this study, then only 6 samples (greater than or equal to 100, and less than 160 ppb) out of the 473 samples analyzed would have required further analysis by HPLC. The organic solvent waste (over 100 L) generated by the HPLC method would have then been reduced to approximately 1.272 L, a considerable time and cost savings in waste management.