New assays for banned substances in cattle rearing The use of growth promoters in farming has been banned throughout the EU for many years. However, it is suspected that corticosteroids are still being used as growth promoters in cattle feeds by certain farmers. Health In an effort to detect and eradicate corticosesteroid use for growth promotion in cattle, the EU focused on the development of novel screening and diagnostic methodologies. Synthetic corticosteroids are being used in animal husbandry to combat inflammatory conditions. Evidence suggests that their use is also intended in certain cases to promote growth, an illegal practice throughout the EU since 1986. In order to detect corticosteroid intake in cattle, project partners developed a new immunoassay covering a number of corticosteroids. In basic terms, an immunoassay measures the amount of specific substances based on their binding to antibodies present in the assay mixture. The CORTICOSTEROID-EIA can be used for the screening of 40 urine samples at a time. It is time efficient, however it offers no clue as to the nature of the specific corticosteroid present. For enhanced specificity, chromatographic and spectroscopic methods can be used. The principle of this particular immunoassay is simple in its conceptualisation. If any corticosteroid amount is present in the urine sample that is being tested then it is bound to the antibodies that coat the assay plate. At the same time, specific enzyme-containing molecules are added to assay plate and these compete with the corticosteroids for the antibody binding sites. The enzyme that is carried by the above-mentioned molecules has the ability to breakdown a specific reagent that is added in later step to the mixture and the product is intensely coloured. On the other hand corticosteroid-antibody conjugates have no affect on the reagent, therefore resulting in no colouration. In other words, the amount of corticosteroids present in the sample is inversely proportional to the observed colour intensity. The EIA assay can be used in a slaughterhouse environment to prove whether or not corticosteroids are being used and to provide indications as to the concentrations. As such, it is likely to constitute an attractive commercial opportunity for agricultural firms and public sector agencies involved in food safety.
