Effects of lighting, stocking density, and access to perches on leg health variables as welfare indicators in broiler chickens

Abstract

An experiment was conducted to investigate the effects of lighting program, stocking density, and the provision of a perch on leg health variables as welfare indicators in broiler chickens. A total of 360 mixed sex Ross 308 1-D-old broiler chickens (180 male and 180 female) were placed in a completely randomized design with 2 × 2 × 2 factorial arrangement of lighting program (continuous or restricted), stocking density (12 or 18 birds/m2), and the provision of a perch (perch or without perch). At d 42, tibial dyschondroplasia (TD), valgus-varus deformity (VVD), footpad dermatitis (FPD), and hock burn (HB) were scored. In addition, tibio-tarsal index, robusticity index, bone weight-length index, tibia crude ash content, and fluctuating asymmetry (FA) and relative fluctuating asymmetry (rFA) of tibia width and length were measured. The incidence of TD increased in broiler chickens subjected to continuous lighting (P < 0.05) in comparison with those subjected to restricted lighting. Presence of a perch reduced the incidence and severity of FPD (P < 0.01) compared to without a perch. Restricted lighting tended (P = 0.093) to decrease the incidence and severity of HB lesions. The broiler chickens placed at low stocking density (12 birds/m2) and with access to a perch had lower incidence and severity of HB lesions (P < 0.01 and P < 0.001, respectively) compared to their corresponding opposite groups. Tibio-tarsal index was greater (P < 0.01) in broiler chickens subjected to restricted lighting regimen compared to continuous lighting whereas the provision of a perch tended to increase (P = 0.081) the tibio-tarsal index in broiler chickens compared to those without perch. There was a tendency of decreasing tibia crude ash content with increasing stocking density from 12 to 18 birds/m2 (P = 0.056). However, birds without perches had greater (P < 0.01) tibia crude ash content compared those with a perch provided. Continuous lighting increased the FA and rFA of tibia length in comparison with restricted lighting program (P < 0.05) in broiler chickens. In conclusion, it can be said that restricted lighting programs and provision of perches may help reduce the leg health problems thus contributing to improved welfare in broiler chickens.