Does social position affect well-being in laying hens?

Abstract

The level of stress is undoubtedly related to the position occupied by an individual in a social group. Research shows that this relationship is complex and can be ambiguous. The study involved 53-week-old 80 Green-legged Partridge hens kept in four independent identical boxes divided by opaque partitions, 20 individuals each. Behaviour was recorded for the following activities: pecking and flight. Behavioural observations began when four flocks were established with combined birds (day 1, 2, 3). Subsequent observations were carried out after the flock structure was established (day 14, 15, 16). Counting was conducted for 8 h/day, 4 h in the morning (6:00–10:00), and 4 h in the afternoon (14:00–18:00). Stress level was assessed using physiological indicators such as steroid hormone levels (serotonin, dopamine, noradrenaline, and adrenaline), corticosterone level and intestinal microflora composition. Changes in group structure were observed and only a small percentage remained constant in terms of belonging to a dominant, subordinate or neutral group. Significant differences in hormone levels were found between birds belonging to the above groups. The results indicated that the lack of an established position in the group structure was a social stressor for laying hens.