The relationship between blood and muscle samples to monitor for residues of the antibiotic enrofloxacin in chickens

Authors: REYES-HERRERA, IXCHEL - University Of Arkansas; Schneider, Marilyn; BLORE, PAM - University Of Arkansas; DONOGHUE, DAN - University Of Arkansas

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2010
Publication Date: 2/1/2011
Citation: Reyes-Herrera, I., Schneider, M.J., Blore, P., Donoghue, D. 2011. The relationship between blood and muscle samples to monitor for residues of the antibiotic enrofloxacin in chickens. Poultry Science. 90:481-485.

Interpretive Summary: In 2005, the United States Food and Drug Administration withdrew approval for use of enrofloxacin in poultry, thus effectively imposing a zero tolerance for residues of this antibiotic in poultry products. Conventional residue monitoring for most antibiotics, including enrofloxacin, involves removing poultry carcasses from the processing line and collecting muscle tissues for analysis. Because of the loss of valuable edible products and difficulties and expense in sampling all the carcasses, only a small portion of carcasses are tested for violative residues. Unlike muscle tissue, blood is readily available from all birds at the beginning of processing and may be used to screen for illegal residues in all poultry carcasses. It is unknown, however, if enrofloxacin concentrations in blood are predictive of muscle concentrations. In an effort to evaluate this relationship, 156 broiler chickens, 5 weeks of age, were dosed with either 25 or 50 µg mL-1 enrofloxacin for 3 or 7 days, respectively, in the drinking water. Blood and muscle samples were collected at 0, 1, 3, 6, 12, 24 hours (n=6 birds/group) during the first dosing day, every 48 hours during the dosing period, and every 12 hours during withdrawal period for up to 60 hours post withdrawal. Enrofloxacin residues were determined in all blood and tissue samples during the dosing periods and most of the withdrawal period for both doses. These results support the potential to use blood to screen for illegal enrofloxacin residues in edible poultry tissues in an effort to protect the human food supply.

Technical Abstract: Use of antibiotics in food animals has generated concern as the presence of these residues in food may contribute to increased microbial resistance in humans. Fluoroquinolone antibiotics are thus now no longer allowed by the U.S. Food and Drug Administration for use in poultry and monitoring of the food supply for fluoroquinolone residues is necessary to ensure compliance. Such monitoring has traditionally been performed using chicken muscle samples, however this approach results in loss of potentially valuable product. Screening chicken blood for fluoroquinolones would avoid this problem and would also facilitate the extraction of any residues present, however the relationship of levels of fluoroquinolones in blood to those in muscle would need to be determined. In this study, chickens were dosed with the fluoroquinolone antibiotic enrofloxacin, and groups of 6 were sacrificed at various time periods over the dosing and withdrawal period. Samples of both muscle and serum were collected from these chickens and analyzed using a bioassay for enrofloxacin. Levels of enrofloxacin in the blood were found to be approximately one half the levels found in the muscle in these samples, except for those containing extremely low concentrations. Determination of this relationship between levels of enrofloxacin in chicken blood and muscle illustrates the potential for screening fluoroquinolone residues in chicken blood as a promising alternative to the use of chicken muscle for monitoring purposes.