title: The residue levels of narasin in eggs of laying hens fed with unmedicated and medicated feed.
abstract: Laying hens were fed contaminated feed containing narasin 2.5 mg/kg for 21 days followed by a 7 day withdrawal period, hens in the control group were fed unmedicated feed. Eggs were collected during trial days 0, 3, 7, 14, 21 and after the withdrawal period of 7 days. The concentration of narasin in yolks and egg whites was analyzed by a liquid chromatography-mass spectrometry method. Narasin was found to accumulate in yolks, where the narasin concentration increased during the treatment. The concentration of narasin varied from 5.9 to 13.8 microg/kg (mean 10.6 microg/kg) in yolks after 21 day feeding periods. The concentrations of narasin ranged from < 0.9 to 1.4 microg/kg after the withdrawal period. Narasin residues were not found in egg whites of the laying hens fed contaminated feed nor in either yolks or egg whites of the laying hens fed unmedicated feed. The effect of cooking was also tested on the amount of narasin residues in eggs. Cooking for 10 min did not significantly influence the narasin residues in eggs. Traces of lasalocid were also found in the yolks. The traces of lasalocid are attributable to an accidental contamination of the feed during its manufacture.
authors.affiliation: National Veterinary and Food Research Institute, EELA, Department of Chemistry, Helsinki, Finland. mervi.rokka@eela.fi
authors.forename: Mervi
authors.initials: M
authors.lastname: Rokka
authors.forename: Susanna
authors.initials: S
authors.lastname: Eerola
authors.forename: Ulla
authors.initials: U
authors.lastname: Perttilä
authors.forename: Laila
authors.initials: L
authors.lastname: Rossow
authors.forename: Eija
authors.initials: E
authors.lastname: Venäläinen
authors.forename: Eija
authors.initials: E
authors.lastname: Valkonen
authors.forename: Jarmo
authors.initials: J
authors.lastname: Valaja
authors.forename: Kimmo
authors.initials: K
authors.lastname: Peltonen
mesh_terms: D000821:Animal Feed; D000818:Animals; D002645:Chickens / Q000378:metabolism*; D003049:Coccidiostats / Q000008:administration & dosage / Q000032:analysis*; D004350:Drug Residues / Q000032:analysis; D004529:Egg White / Q000032:analysis; D004530:Egg Yolk / Q000737:chemistry; D004531:Eggs / Q000032:analysis*; D005260:Female; D005506:Food Contamination / Q000032:analysis*; D006358:Hot Temperature; D011714:Pyrans / Q000008:administration & dosage / Q000032:analysis*
chemical_list: D003049:Coccidiostats; D011714:Pyrans; C013612:narasin