Association between plumage condition and fear and stress levels in five breeds of chickens.

Duration of tonic immobility and heterophil to lymphocyte ratio (indices of fear and stress, respectively) were compared in hens having very poor or perfect plumage at 72 wk of age. Five Spanish breeds of chickens (Castellana, Andaluza, Vasca, Villafranquina, and Leonesa) were used. There were significant differences among groups in terms of tonic immobility duration and heterophil to lymphocyte ratio (P < 0.05). Very poorly feathered hens showed shorter tonic immobility (243.03+/-26.81 s) and higher leukocyte ratio (0.42+/-0.02) than did hens with a perfect plumage (322.32+/-26.81 s and 0.35+/-0.02, respectively). Differences were consistent across the breeds. Thus, hens with very poor plumage were less fearful and more stressed than hens with a perfect plumage. The results suggest that very poor plumage is associated with indicators of fearfulness and stress.