Residues of an anabolic treatment: trenbolone acetate and zeranol in steers

Longhi, A.; Benedetto, M. di; Berra, G.; Lucas, C.

Revista Argentina de Produccion Animal 14(1/2): 121-129


Accession: 002944738

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The authors studied, for 54 days, the residue accumulation-elimination curve in the liver and urine of a steer implanted with 200 mg of trenbolone (TBA) and 36 mg of zeranol (Zer). Radioimmunoassay (RIA) was used to measure the levels of 17- alpha trenbolone (17- alpha TBOH), 17- beta trenbolone (17- beta TBOH) and Zer in samples of tissues, urine and bile obtained from 2 steers implanted with these anabolics when killed 61 days after treatment. Liver residues of 17- alpha TBOH increased with time, while Zer levels remained almost constant during the 54 day experiment. Urine levels varied erratically with the 17- alpha TBOH always >1 micro l/litre while Zer levels were sometimes greater and the 17- beta TBOH levels were always lower. When the animals were killed no anabolic residues could be detected in the muscles. In the liver the concentrations of 17- alpha TBOH, 17- beta TBOH and Zer were 1.51-2.82, 0.28-0.33 and 1.01-2.22 micro g/kg respectively. The concentrations in the kidneys were 0.11-0.13, 0.08-0.13 and 0.31-0.36 micro g/kg. Biliary concentrations of 17- alpha TBOH and Zer were 804-499 and 71-88 micro g/litre respectively. It is concluded that the liver is the target organ for both anabolics; that urine samples are unsuitable for monitoring Zer levels, and that biliary excretion is an important route of elimination for the 2 anabolics.