Research note: Effects of scalding on feather corticosterone concentrations in broiler chickens

Feather corticosterone concentrations (fCORT) can be used to provide insights into long-term stress over the feather growth period in poultry and has potential to be included in routine assessment of animal welfare. While this measure is validated in broiler chickens, it is unclear how slaughter and processing procedures would influence fCORT assay outcomes. The objective of this study was to determine whether the scalding process at slaughter would impact corticosterone concentrations in broiler chicken feathers using Enzyme-Linked Immunosorbent Assays (ELISA). Broiler chickens were commercially raised on pasture and slaughtered at eight weeks of age. Primary feathers (P7) from 24 arbitrarily chosen broilers were collected prior to and after the scalding process to assess feather corticosterone (fCORT) concentration (feather n = 48) using ELISA. One broiler (2 feather samples) was excluded from the dataset (final n = 23 broilers). The mean fCORT concentrations were lower (paired t-test: p < 0.001) post-scalding (8.34 pg/mm) compared to pre-scalding (11.40 pg/mm), with fCORT concentrations decreasing in 20, and increasing in 3 broilers post-scalding. Our findings indicate that the scalding process, an inherent part of broiler chicken processing at slaughter, does impact fCORT assay outcomes, likely due to the agitation damaging the feather structure, releasing fCORT into the water. This suggests that as part of an animal welfare assessment, feather samples should be collected prior to scalding to obtain a biologically representative indication of long-term stress experienced during the period of feather growth, rather than after scalding, unless the fCORT concentrations will be used as a relative rather than absolute indicator of animal welfare.