Modern broiler chickens have been selectively bred for extreme growth rates, causing widespread leg disorders, cardiovascular disease, and chronic pain. Up to 30% of UK broilers show moderate to severe lameness before slaughter.
Lame broilers walk less, feed less, drink less, and show behavioural signs of pain. Research using pain relief medication demonstrates that lame birds eat more when given analgesics, confirming chronic pain. The welfare harm is systemic and pervasive, affecting the majority of the 1 billion chickens produced in the UK annually. Conventional indoor systems with standard breeds represent one of the largest animal welfare problems by number of individuals affected.