Applied research note: Optimized corticosterone extraction following feather dissolution by keratinase

The study aimed to develop and validate a robust, non-invasive method for assessing corticosterone (CORT) concentrations in poultry feathers as an indication of lifelong stress. Traditional sample preparation using methanol extraction showed high variability, prompting the exploration of a keratinase-based protocol. Three protocols were compared: methanol extraction (MP), original keratinase (KP), and an optimized keratinase protocol (OKP). The OKP significantly reduced intra-assay variability to 5.4 % compared to 61 % (MP) and 33 % (KP). Feather CORT levels were reliably quantified using the OKP, showing linear recovery of spiked samples (R² = 0.97). No significant correlation was found between plasma and feather CORT concentrations, underscoring the potential of feather sampling for long-term, as opposed to acute, stress assessment in poultry. This optimized method provides a valuable tool for animal welfare studies, enabling accurate and consistent measurement of feather CORT levels across different poultry strains and conditions.