Confirmation of protein biomarkers of corticosteroids treatment in veal calves sampled under field conditions.

In veal calf production, growth promoters are still illicitly used. Surveillance of misuse of such molecules is necessary to preserve human health. Methods currently adopted for their analysis are based on liquid chromatography tandem mass spectrometry, but their efficacy can be affected by undetectable residual concentrations in biological matrices due to treatments at low-dosage or based on unknown anabolic compounds. The development of screening methods to identify the indirect biological effects of administration of growth promoters can improve the efficiency of drug residue monitoring. To this purpose, an integrated approach has been used to further validate the set of protein biomarkers defined in a previous controlled study to detect the use of corticosteroids through the changes caused in muscle protein expression. The thymus morphology of 48 samples collected under field conditions was evaluated to assess the presence of potential corticosteroids treatment. Animals were divided on the basis of their thymus characteristics in negative or suspected for illegal corticosteroids treatment. Drug residue analyses were performed on the liver, giving a satisfactory correlation with the histological examination (similar to 85%). Finally, the proteomics analysis of muscle protein extracts was carried out by 2D differential in gel electrophoresis, and proteins that were differentially expressed between the two animal groups (p value <0.01) were selected for MALDI-MS/MS analysis. This approach allowed us to identify 29 different proteins, and our findings indicate that the altered protein expression pattern can be used as an indirect method for the detection of illicit corticosteroids administration. A subset of the identified proteins was already reported in a previous controlled study, proving that these biomarkers can be used to develop a screening assay to improve the tools currently available for the detection of corticosteroids abuse in bovine meat production.