title: Evaluation of thymus morphology and serum cortisol concentration as indirect biomarkers to detect low-dose dexamethasone illegal treatment in beef cattle.
abstract: BACKGROUND
  Corticosteroids are illegally used in several countries as growth promoters in veal calves and beef cattle, either alone or in association with sex steroids and β-agonists, especially at low dosages and primarily through oral administration, in order to enhance carcasses and meat quality traits. The aim of the present study is to evaluate the reliability of the histological evaluation of the thymus, as well as the serum cortisol determination, in identifying beef cattle, treated with two different dexamethasone-based growth-promoting protocols and the application of different withdrawal times before slaughter.
  
  
  RESULTS
  Our findings demonstrate that low dosages of dexamethasone (DXM), administered alone or in association with clenbuterol as growth promoter in beef cattle, induce morphologic changes in the thymus, resulting in increase fat infiltration with concurrent cortical atrophy and reduction of the cortex/medulla ratio (C/M). In fact, the C/M value was significantly lower in treated animals than in control ones, with both the protocols applied. The cut off value of 0.93 for the cortex/medulla ratio resulted to be highly effective to distinguish control and treated animals. The animals treated with DXM showed inhibition of cortisol secretion during the treatment period, as well as at the slaughterhouse, 3 days after treatment suspension. The animals treated with lower doses of DXM in association with clenbuterol, showed inhibition of cortisol secretion during the treatment period, but serum cortisol concentration was restored to physiological levels at slaughterhouse, 8 days after treatment suspension.
  
  
  CONCLUSIONS
  The histological evaluation of thymus morphology, and particularly of the C/M may represent a valuable and reproducible method applicable to large-scale screening programs, due to the easy sampling procedures at slaughterhouse, as well as time and cost-saving of the analysis. Serum cortisol determination could be considered as an useful in vivo biomarker of dexamethasone illegal treatment in beef cattle during the fattening period, whilst it does not appear to be a good biomarker at the slaughterhouse, since the protocol of DXM administration, as well as the withdrawal period could affect the reliability of the method.
authors.affiliation: Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy. mvascellari@izsvenezie.it
authors.forename: Marta
authors.initials: M
authors.lastname: Vascellari
authors.forename: Katia
authors.initials: K
authors.lastname: Capello
authors.forename: Annalisa
authors.initials: A
authors.lastname: Stefani
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Biancotto
authors.forename: Letizia
authors.initials: L
authors.lastname: Moro
authors.forename: Roberto
authors.initials: R
authors.lastname: Stella
authors.forename: Giandomenico
authors.initials: G
authors.lastname: Pozza
authors.forename: Franco
authors.initials: F
authors.lastname: Mutinelli
mesh_terms: D000818:Animals; D015415:Biomarkers; D002417:Cattle / Q000097:blood*; D003907:Dexamethasone / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D006133:Growth Substances / Q000032:analysis; D006854:Hydrocortisone / Q000097:blood*; D012680:Sensitivity and Specificity; D015813:Substance Abuse Detection / Q000379:methods / Q000662:veterinary*; D013950:Thymus Gland / Q000187:drug effects* / Q000473:pathology
chemical_list: D015415:Biomarkers; D006133:Growth Substances; D003907:Dexamethasone; D006854:Hydrocortisone