Effects of environmental enrichments applied to pasture areas on free-range laying hens: 2. Pasture use, behaviour and welfare

This study assessed the effects of environmental enrichment on outdoor ranges for birds aged either 25, 36, 48 and 56 weeks on pasture use, behaviour and welfare of free-range laying hens. In total, 900 hens (25 weeks old) were randomly divided into three groups (control, object enrichment and tree enrichment) with three pens each (100 hens/pen). Each group was provided with a closed shelter and pasture range nearby.2. A control (CON) group of birds was maintained without any extra enrichment. Various rectangular, square, cylindrical and triangle shaped boxes, pipes, buckets and structures in yellow, red and orange colour were used for the ‘object’ (OBJ) enrichment treatment, whereas tall and broad-leaved plants and Thuja trees were used for the ‘tree’ (TREE) enrichment treatment.3. The use of total pasture area in hens was not different amongst enrichment treatment groups or bird age. While the proportion of OBJ hens using the inner zone of the pasture was higher (p < 0.01), CON and TREE hen groups were found more in the outer zone of the pasture (p < 0.01).4. Enrichment treatment and age did not affect blood heterophil, lymphocyte and heterophil/lymphocyte (H/L) ratio. Feeding, drinking, walking, foraging, resting/laying, perching, scratching/preening and pecking behaviours were not different between enrichment treatment groups. Hens exhibited more feeding, drinking, walking, foraging and less perching, scratching/preening and pecking behaviours with age (p < 0.01).5. There were no differences in feather condition, comb wounds, foot pad dermatitis, keel bone damage, duration of tonic immobility or induction number amongst the enrichment groups. Older hens were showed significant deterioration in feather condition, increased occurrence of comb wounds, footpad dermatitis, hock burns and keel bone damage (p < 0.01). These findings indicated that environmental enrichment can increase the use of a specific area of the pasture where objects are used for enrichment.