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(40-15) Degradation Kinetic of Doxycycline in pig manure. Alonso, Carmen*,1, Fernández, Carlos1, del Río, Carmen1, García, Pilar1, Carbonell, Gregoria1, Tarazona, José1, 1 Laboratory for Ecotoxicology Department of Environment. INIA, Madrid, Spain ABSTRACT- The use of veterinary drugs in food producing animals is a usual practice. As a consequence, the presence of these drugs residues and/or their metabolites in livestock manure must be considered in the evaluation of the environmental risk when pig manure are used as agricultural amendments. Doxycycline is a wide spectrum antibiotic molecule which, in mammals, is excreted intact. Therefore, its presence in urine and faeces from treated livestock is expected. This work studies the degradation kinetic of Doxycycline, in a 30 days period in a pig manure fortified with a nominal concentration of 75 mg/l, calculated from dosage (12 mg/kg b.w./day), animal weight (90 kg), manure production (4.75 l/day) and 100% elimination rate. The analytical methodology used was SPE (Solid phase extraction OASIS, Waters), followed by HPLCRP-DA (Waters 2695-2696). This is a simple and robust method that permits quantification of Doxycycline in complex environmental samples showing good recovery and repeatability figures. The results obtained clearly show a rapid decrease of the Doxycycline initial concentration reaching the stationary step in 72 hours. This quick slope down of the Doxycycline could be due to a dissipation process rather than a biological degradation. This fact was confirmed following the same experiment with the pig manure contaminated with a Doxycycline concentration 100 times higher. This study has been founded by the research project UE ERAV-EVKI 1999-00034P and a research collaboration with LABORATORIOS HIPRA S.A. (SPAIN). Key words: Pig manure, Doxycycline, Degradation kinetic, HPLC |
