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This study investigates the influence of low dosages of /I-agonists combined with other growth promoters on screening and confirmation methods in male veal calves. Five groups of four calves were treated for 6 weeks with combinations of low dosages of B-agonists (BAG, clenbuterol, mabuterol and mapenterol, 0.4pg/kg each twice daily) in combination with 17P-estradiol (E2, 5mg per animal per 14 days), methylthiouracil (MTU, 2.857mg/kg bw twice daily) and dexamethasone @EX, 4mg per animal per 10 days during the last 20 days of treatment). Another group of four untreated animals served as controls. The weight and sue of the thymus was reduced in the DEX group, the MTU group showed enlarged thyroids. Histologically the prostates showed vacuolar degeneration in the BAG animals and metaplasia in the E2 group. Some vacuolization was also observed in the controls. The testis.showed impaired development in all treatment groups, E2 leading to the most severe changes. DEX led to cortical atrophy of the thymus. MTLJ induced hyperplastic changes in the thyroid. These results indicate that comedication does not markedly affect the histological changes induced in the hormonal target tissues. For screening purposes histology of the prostate can be used as a marker for oestrogens, whereas the weight of the thymus and thyroid can be used as an indication for the use of corticosteroids and thyreostatics, respectively. Vacuolization in the prostate appeared no reliable indication for B-agonists. Samples of urine, faeces, liver and eye (cetina/choroid) were analysed for 1-agonists. E2 significantly increased the levels of all 8-agonists in the liver and faeces, whereas DEX significantly reduced these levels. These observations show that additional medication with different groups of growth promoters can markedly alter the excretion of 8-agonists and thus influence (regulatory) control.

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To investigate the possibilities for screening and confirmation methods when the 'pour on' method of application is used for administration of growth promoters, an animal experiment was performed using a cocktail of a combination of growth promoters derived from (illegal) practice. Two cocktails were used, cocktail A consisting of stanozolol and estradiol benzoate and cocktail B consisting of stanozolol, estradiol benzoate and beclomethasone dipropionate. The intended dose per animal was 110 mg stanozolol, 25 mg estradiol and 10 mg beclomethasone. The experiment was performed on 20 male veal calves, 16 treated and 4 vehicle treated controls and 3 female veal calves, 2 treated and 1 vehicle treated control. Half of the animals were shaven prior to the application of the drugs. The cocktails were administered using two types of vehicles: vehicle A; Miglyol 840 with butylated hydroxytoluene and vehicle B; di(ethyleneglycol) monobutylether. During a 28 day treatment period, one group of animals was treated once a week, another group of animals was treated once every two weeks and slaughtered. Preliminary results showed that pour on application of anabolic steroids markedly increased growth performance of veal calves, the animals treated with cocktail A performed better than the animals treated with cocktail B. Macroscopically, the thymus was reduced in weight and size in the B animals. The bulbo-urethral glands were enlarged in all treated animals. Histologically all treated animals showed squamous metaplasia in the prostate, bulbo-urethral gland and Bartholins glands. Moreover, a changed secretion pattern was observed in both the prostate and the bulbo-urethral gland. Severe cortical atrophy was observed in the thymus and to a lesser extent the adrenals of the beclomethasone treated animals. The recently discovered 16 beta-hydroxy-metabolite of stanozolol was detected in urine, in relatively high concentrations. This is the first report of the excretion of this metabolite in urine after pour on administration showing the prospect for detection of dermal treatment. Estradiol levels were remarkably elevated (up to 200 micrograms l-1) exceeding the endogenous levels (< 1 microgram l-1).