Modern broiler breeds grow from hatch to market weight (2.5 kg) in 35-42 days — a 400% increase in growth rate over 60 years. Fast-growing breeds show elevated rates of leg disorders (tibial dyschondroplasia, valgus/varus deformity), cardiac disease (SDS, ascites), and restricted locomotion. Mortality in fast-growing broilers is 3-5× higher than slow-growing breeds.
Slow-growing breeds (Hubbard JA57, Cobb Sasso, Ranger Classic) take 56-70 days to reach market weight. Research consistently shows superior welfare: lower leg disorder prevalence, better locomotion scores, more time active, and lower mortality. The EU Better Chicken Commitment (signed by 400+ companies) requires slow-growing genetics by 2026 for signatories.
EU Directive 2007/43/EC allows stocking densities up to 33 kg/m² (with derogation to 42 kg/m²). Research shows significant welfare improvement below 30 kg/m². At lower densities, birds spend more time walking, dustbathing, and resting in preferred positions. Severe crowding restricts movement, increases aggression, and worsens litter quality.
Broilers spend 70-80% of time resting or sleeping, but their quality of waking behavior matters significantly for welfare. Perches, pecking objects, and natural light cycles improve behavioral welfare. Litter quality — maintaining dry, friable substrate — is essential for foot health (contact dermatitis prevention) and dustbathing.
Most broilers are slaughtered using electrical waterbath stunning. Welfare concerns arise from pre-stun shackling (birds hung inverted while conscious — up to 4 minutes), and from stunning failure. Controlled atmosphere killing (nitrogen, CO2/argon mixtures) applied in the shed before transport eliminates pre-slaughter handling stress and is increasingly used by high-welfare producers.
The Welfare Quality® protocol provides validated broiler welfare measures: gait score (locomotion quality 0-4), hockburn prevalence, footpad dermatitis, feather cover, plumage cleanliness, and behavior observations. Integrating welfare outcome data into flock monitoring systems enables targeted intervention at farm level.