Stability of zeranol, nandrolone and trenbolone in bovine urine.

The stability of some growth promoting agents in cattle urine, under various temperature storing conditions, was investigated. Bovine urine samples obtained from previous excretion studies which contained zeranol, nandrolone and trenbolone respectively, were stored frozen, at room temperature and in direct sunlight. On days 0, 2, 4, 7 and 10, zeranol and nandrolone were quantified by selective ion monitoring analysis on a gas chromatography-mass selective detector and trenbolone by using an enzyme linked immunosorbent assay. Zeranol and its metabolite taleranol are stable under all of these storage conditions. There is a remarkable decrease in the concentration of 17 alpha-19-nortestosterone, the main metabolite of nandrolone in cattle, when stored at room temperature and in direct sunlight. There is also a decrease in concentration of trenbolone when stored in direct sunlight. From the results it can be concluded that urine specimens obtained from cattle for residue analysis should be frozen as soon as possible after collection.