Assessment of fear response and welfare indicators in laying hens from barn systems

This study aims to evaluate the association of body weight (BW) and age on welfare indicators and fear response (tonic immobility (TI) duration and number of TI induction trials) and the relationships among welfare indicators. At 50 and 72 weeks of age, 100 laying hens (Novogen brown) from barn systems were weighed and tested for tonic immobility (TI). After that, a physical examination was carried out to evaluate health condition, hygiene status, feather damage and claw length. Most welfare problems detected at 50 weeks had increased by 72 weeks of age. A higher score for keel bone protrusion was observed in lighter (BW <= 1.9 kg, P = 0.014) and older hens (72 weeks, P = 0.004). Heavier hens (BW > 1.9 kg) showed longer TI durations (P = 0.022) and older hens required fewer TI inductions (P = 0.025), indicating that heavier and older hens were more fearful. Feather damage score on wings was positively correlated with feather damage scores on back, rump and tail (P < 0.001). Hens with higher feather damage scores on the head, back and tail showed a higher probability of having longer TI durations. Hens with skin injuries (W = 4.100, P = 0.043) were more likely to be induced into TI on the first attempt. Hens with higher feather damage scores on head, back and tail and increased skin injuries were considered more fearful. Additionally, high cumulative mortality rates (23-26%), keel bone deformations (57%) and keel bone protrusion (89%) should be considered relevant welfare indicators in laying hens from barn systems.