Formation of anhydrotetracycline during a high-temperature treatment of animal-derived feed contaminated with tetracycline

Residues of tetracyclines and their epimers were frequently found in bones of slaughtered animals, and also in meat and bone meals for animal feed tha t had been heat treated according to EU legislation. The aim of this study was to examine the formation of anhydrotetracycline and 4-opianhydrotetracy cline, as toxic degradation products of tetracycline, during a heat treatme nt, Meat and bone meals containing bound tetracycline residues were heat tr eated at 100 and 133 degreesC for up to 45 min, extracted with hydrochloric acid and subsequently analyzed for tetracycline, 4-epitetracycline, anhydr otetracycline and 4-epianhydrotetracycline, using HPLC and LC-MS-MS. Small amounts of anhydrotetracycline and 4-epianhydrotetracycline were even found in the pre-treatment control samples. The heat treatments led to a signifi cant increase of the amounts of these degradation products. During the most rigorous heat treatment, at 133 degreesC for 45 min, the mean percentage d ecrease of the concentrations of tetracycline and 4-epitetracycline was 50% , while the mean percentage increase of the concentrations of anhydrotetrac ycline and 4-epianhydrotetracycline was 533%. (C) 2001 Elsevier Science Ltd . All rights reserved.