Investigating feather corticosterone and fault bars along the length of domestic male turkey (Meleagris gallopavo) feathers

Fault bars are visible deformities in the feather structure potentially related to the stress response and may be an interesting trait that can reflect robustness. This study's objective was to describe fault bars along the length of domestic turkey feathers and investigate whether fault bars are associated with feather corticosterone (FCORT). The same primary wing feather was evaluated from 75 male turkeys from three genetic lines. Feathers were cut into three (proximal, middle, and distal) sections to score fault bar presence, incidence, and severity. FCORT was measured for each feather section using ELISA. Linear mixed models were used to investigate differences in the fault bar presence, incidence, and severity between feather sections and genetic line, as well as investigate associations between the fault bar measures and FCORT. There was a significant increase in FCORT and fault bar incidence from proximal to distal feather sections (P < 0.0001). In the distal section only, sections with fault bars had significantly higher FCORT compared to sections without fault bars (P = 0.0088). No associations were found between fault bars and FCORT in the other sections. Consequently, associating FCORT and fault bars using whole primary wing feathers may be challenging. Future work should reevaluate this relationship longitudinally to better understand fault bar development.