Chlortetracycline residues in pigs after oral application of the chlortetracycline feed grade preparation (Biotika)

Dvorak, M.; Miller, V.; Hlavizna, L.-Vv-Janeckovaan; Benuska, M.-Norbert

Biopharm 3(3-4): 91-102


ISSN/ISBN: 0139-8571
Accession: 008311021

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We have monitored chlorotetracycline (CTC) concentrations in the blood serum and CTC residues in tissues (muscles, liver, kidneys and fat) after a continuous application of three doses-3.5 mg, 30 mg and 60 mg/kg a day during six days in a series of three experiments with pigs, whose average weight was 22 and 25 kg. The antibiotic was applied in the fodder in the form of Chlorotetracycline feed grade preparation (Biotika). We have used the microbiologic method (B. Cereus) of monitoring therapeutic levels in the blood serum during the six days of application and the enhanced HPLC method with sensitive and specific fluorescence detection (quantitative limit of 5 ng/g, recovery of 83% with the variation coefficient 8.6% and reproducibility variation coefficient 1.9%) for monitoring residues in tissues. In the first experiment we have monitored residues of a dose of 20 mg/kg in 1, 3, 7, 10, 14 and 21 days after the end of application. Three pigs were treated in each sampling, all samplings showing low residues. Residues dropped under the maximum residual limits (MRL) in four days. The withholding time is therefore 4 days. In the second and third experiment we have monitored residues after doses of 3.5 mg/kg and 60 mg/kg in 1, 3, 7, 14 and 28 days after the application. Infinitesimal residues-lower than MRL-were observed even after the dose of 3.5 mg; no withholding time, however, is necessary. Residues after the dose of 60 mg/kg dropped under MLR values on the 7th day (residues in kidneys). The withholding time is therefore 7 days. The following values were made out by the means of microbiological monitoring of therapeutically effective levels in the blood serum during a 144 hours long application: the dose of 3.5 mg/kg produced only rare and infinitesimal levels (0-91 mu-g/l); the dose of 20 mg/kg produced relatively low levels in the range of 124-354 mu-g/l and the dose of 60 mg/kg produced slightly higher concentrations in the range of 174-1010 mu-g/l (average of 506 mu-g/l). These CTC concentrations can prove to be efficacious against highly or medium sensitive bacterial strains.