Production and stability testing of incurred reference materials for the anabolic steroid trenbolone in bovine urine.

The production of stable reference materials with incurred residues of veterinary drugs is necessary for the validation of methods of analysis, including the determination of critical performance characteristics. A reference material for trenbolone in bovine urine was produced and the long-term stability was tested. From a pilot 16 week stability study on seven batches containing different additives it was concluded that the use of preservatives does not improve the stability of the residue. A final batch of reference material of 800 vials each containing 5 ml of urine with a target concentration of 5 micrograms l-1 was prepared. The homogeneity and long-term stability of the material were tested. The material was found to be homogeneous. Based on the results of a 52 week stability study it was concluded that the material is stable, using the current analytical methodology. For the development of reference materials, highly accurate and precise analytical methods are necessary. However, the current analytical methodology is not suitable for full evaluation and certification. Currently, a new LC-MS method is being developed. After validation of this method, the stability and homogeneity study will be repeated.

Comparative effectiveness of somatotropin and anabolic steroids in feedlot steers.

Crossbred steers (n = 252, BW = 379 +/- 28 kg) were allotted to 42 pens in a 2 x 3 factorial arrangement of treatments: control or steroid implant (STR; estradiol benzoate+progesterone [three lighter blocks reimplanted on d 84] and trenbolone acetate [reimplanted on d 63]), and either 0, 80, or 160 mg/wk of recombinant bovine somatotropin (bST). Steers were adapted to the finishing diet (12% roughage equivalent, 13% CP) before the start of the experiment and fed for 84 or 119 d. Blood samples were taken on d 0, 14, 28, 56, and 84 for plasma urea N (PUN), serum somatotropin (ST), plasma insulin-like growth factor I (IGF-I), and plasma amino acid assay. Few interactions were noted (P > .1). Gain was increased by both treatments: 1.30 vs 1.66 kg/d for control vs. STR (P < .001) and 1.44, 1.49, and 1.51 kg/d (linear, P = .07) for 0, 80, and 160 mg of bST/wk, respectively. Gain efficiency was also improved: 169 vs 205 g/kg (P < .001) and 177, 189, and 195 g/kg (linear, P < .001), respectively. Average PUN was decreased (P < .001) 29% by STR and decreased 17 and 29% by 80 and 160 mg of bST/wk, respectively (linear, P < .001). Somatotropin decreased mean serum ST compared with controls; STR increased ST 36% compared with controls. Average plasma IGF-I was increased (P < .001) 12% by STR and 13 and 19% (linear, P < .001) by 80 and 160 mg of bST/wk, respectively. Both STR and bST influenced (P < .05) plasma amino acid profiles. Indicators of carcass fatness were decreased linearly (P < .05) by bST; STR implant tended to decrease carcass fatness and increase longissimus muscle area, which was related to carcass weight. The anabolic effects of STR and bST were found to be additive and possibly independent in feedlot steers.