Measuring feather and plasma corticosterone in male broiler chickens: uplc–ms/ms methodology and feather growth dynamics

Plasma corticosterone (CORTp) is widely used to assess acute stress in chickens, while feather corticosterone (CORTf) has been investigated as a marker of cumulative corticosterone (CORT) exposure during feather growth. The objectives of this study were: (1) to validate an Ultra Performance Liquid Chromatography coupled to Tandem Mass Spectrometry (UPLC-MS) to evaluate measurements of CORTp and of CORTf in different type of feathers (dorsal, wing, and tail) in broiler chickens; (2) to determine at different ages whether higher exposures to chronic exogeneous administration of CORT increases CORTf and CORTp; (3) to evaluate the correlation between CORTf and CORTp; (4) assess the effects of increased CORT exposure on body weight (BW) and feather morphology, exploring whether structural changes might influence CORT deposition. A UPLC-MS/MS method previously established for CORTp quantification was revalidated for application in the present study, and a new method for CORTf quantification was developed and fully validated. Sixty broiler chickens received incrementally larger daily oral doses (0–5 mg/kg) of CORT from day 1 to 42 to model prolonged elevated circulating CORT. At days 14, 28, and 42, plasma and feathers were sampled and analysed to quantify CORTp and CORTf. BW was recorded daily, and wing feather morphology was assessed macroscopically at 42 days. Data analysis included linear regression, polynomial contrasts, Pearson correlations, and log transformation for feather data. The UPLC-MS/MS methods were validated for quantifying both CORTp and CORTf. By 42 days of age, CORTf increased proportionally to the higher CORT exposure levels across all feather types, and CORTp likewise showed a significant rise at this age. A moderate positive correlation was found between CORTp and CORTf at 42 days. Results showed a negative linear relationship between CORT exposure dosage and BW, as well as with wing feather growth; rachis length was notably shorter in birds exposed to higher CORT doses. Although oral dosing does not replicate the dynamic endocrine profile of a natural stress response, our findings show that CORTf partially reflects circulating CORT during feather growth, though not in a dose-dependent manner, and that prolonged elevation of CORT impairs growth and feather development in broilers.