Corticosterone in Feathers of Laying Hens: An Assay Validation for Evidence-based Assessment of Animal Welfare

ABSTRACT Studies indicate that the evaluation of animal welfare in birds may be carried out with the measurement of the stress-related hormone corticosterone in feathers. However, a standardized procedure for corticosterone measurements in feathers is lacking, a validation needs to be carried out for each new species before implementation. The aim of the current study was to establish a valid method to measure corticosterone concentrations in feathers of laying hens in a precise and repeatable manner using an established and commercially available ELISA. Validation was performed with feather pools of tail and interscapular feathers of commercial Lohmann Brown laying hens. Assessment groups, consisting of five replicates, were created. All replicates of an assessment group were processed at the same time. Each replicate was run in four repetitions with an ELISA. Intra- and inter-assay coefficient of variation was 7.5 % and 6.4 %, respectively. The serial dilution showed linearity and parallelism. Examining the hormone extraction efficiency by using different methanol volumes resulted in no statistical differences (P > 0.05). Pulverized feathers showed higher corticosterone values than minced feathers (P > 0.05). Differences were shown between two feather types (tail vs. interscapular feathers; P 0.05). With the present study a valid protocol, feasible for analyzing feather pools of laying hens, was developed. It may provide fundamentals for further investigations on corticosterone in feathers as a noninvasive indicator to evaluate aspects of animal welfare.