The performance of three conventional enzyme and radioimmunoassays routinely used to detect residues of anabolic steroids in cattle sera were compared with dissociation enhanced lanthanide fluorescence immunoassay (DELFIA) kits designed for the hospital market. Slight modifications to the kit reagents were required for the analysis of bovine sera. Owing to the large sample volumes used in conventional assays, detection limits were generally better than those obtained with DELFIA kits, however, assay reproducibility was enhanced using the DELFIA technology. Comparison of sera obtained from cattle implanted with anabolic steroids revealed a good correlation between alternate methods (r2 from 0.91 to 0.97). The DELFIA kits offer a faster method for measuring estradiol, progesterone and testosterone with adequate sensitivity and in a safer environment than that encountered using radioimmunoassays.

Reports of the illegal use of clenbuterol as a growth promotant prompted the development of a competitive enzyme immunoassay for this drug. This procedure was utilized to study the elimination of clenbuterol from tissues in sheep medicated with both therapeutic and growth-promoting doses of the drug. The results indicated that prior to removal of medication clenbuterol was widely distributed throughout the animal tissues. However as the withdrawal periods increased fluid targets such as urine and bile became less effective at detecting clenbuterol usage. At both therapeutic and growth-enhancing concentrations of clenbuterol liver samples remained positive up to the maximum withdrawal time given in this experiment (15 days). Concentrations of clenbuterol likely to cause food poisoning (> 100 ng/g) were only detected in liver samples taken prior to the removal of medication. The highest recorded concentration of clenbuterol in muscle was 22.5 ng/g.

The administration of anabolic steroids, for the purposes of growth promotion, to food-producing animals is banned in the EU. Among the compounds covered by this prohibition is ss-nortestosterone (beta-NT). This hormone is known to occur naturally in stallions and boars, and its main bovine metabolite, alpha-nortestosterone (alpha-NT), occurs naturally in pregnant cows and neonatal calves. However, neither compound is believed to occur naturally in male cattle. During 2006, the presence of alpha-NT and, on occasion, beta-NT was confirmed in male cattle (bulls and steers) slaughtered in Northern Ireland on welfare grounds, as a result of acute injury. Subsequent investigations revealed no evidence of abuse at any of the farms involved and revealed that the phenomenon also occurred in three other regions of the EU, in similarly injured animals. A hypothetical link to release of the adrenal steroid, dehydroepiandrosterone (DHEA), in response to the stress of the injury was tested. Following the intravenous administration of DHEA to two normal steers, beta-NT (but not alpha-NT) was confirmed in the urine of one steer. Thus, it may be concluded that both beta-NT and, by implication, alpha-NT can occur naturally in male cattle (or a specific cohort thereof) in contrast to previously accepted scientific knowledge.

Laboratory testing in N. Ireland for the illegal growth promoting agent, clenbuterol (CBL), is centralized at the Veterinary Sciences Division, Belfast. During the past 6 years a variety of testing schemes have evolved to determine the level of abuse of this drug in the local meat industry. The types of samples from cattle tested during this period altered as pharmacokinetic data for the compound increased. Initially, fluids such as urine and bile were used, however testing switched to more appropriate tissues such as liver, eyes, and hair. The first positive samples were detected in 1990, with 43 out of 121 samples tested showing detectable residues. In the following year, this number increased to 139 out of 286 tests. Despite substantial increases in the number of samples analysed over the succeeding years, the numbers of positive results steadily declined, thus giving strong evidence that abuse was also on the decline. From the data collected over the 6-year period, it became clear that the EU National Surveillance Scheme designed to detect abuse of illegal substances was ineffective and locally designed programmes were required to effectively tackle the problem.