Brown and white egg-layer strain differences in fearfulness and stress measures

Abstract Different genetic lines of laying hens may show varying levels of fearfulness in response to stressful events or situations. It is important to select appropriate genetic strains when keeping hens in alternative housing systems to minimize health and production issues caused by fear and stress. In this study, data were obtained from two strains of Rhode Island Red (RIR1-2), two strains of White Plymouth Rock (WPR1-2) and three strains of White Leghorn (WL1-3) breeds. One hundred hens from each strain were used to compare strain differences in fear and stress responses. Each hen was scored for fearfulness based on her responses to the following tests: novel object, physical restraint, pencil, human reaction, inversion, and tonic immobility (TI). Stress was assessed based on physical asymmetry (ASYM) of the metatarsal and middle toe, and on corticosterone (CORT) concentrations in blood plasma and egg albumen. Differences between brown (RIR; WPR) and white (WL) egg layers were observed for all measures: WL had more head movements and took more time to right themselves during TI (P