Abstract
BackgroundCorticosteroids 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.ResultsOur 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.ConclusionsThe 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.
Highlights
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
Chemical analysis The analytical methods fulfilled the European requirements and were considered adequate for the analytical purposes of this study; in particular, recovery was better than 95%, precision was lower than 6.5% and calculated decision limits (CCα) were 0.251 μg/L in urines, and 0.247 μg/Kg in liver
Our findings demonstrate that low dosages of DXM, administered alone or in association with clenbuterol as growth promoter in beef cattle, according to the protocols often illegally adopted in farm practice [7], induce morphologic changes in the thymus, resulting in increase fat infiltration with concurrent cortical atrophy
Summary
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. Corticosteroids are illegally used in several countries as growth promoters in veal calves and beef cattle, either alone or in combination with anabolic agents, especially at low dosages and primarily through oral administration, in order to enhance carcasses and meat quality traits [1,2]. These drugs are usually used in association with sex steroids and β-agonists to obtain a higher proportion of lean meat [3]. In adult cattle, it is difficult to distinguish between the physiological rate of involution and the atrophy induced by treatment
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