Modern broiler chickens have been bred for such rapid growth that their bodies frequently cannot keep pace. Skeletal disorders, heart failure, and lameness are the direct result — causing enormous welfare harm at scale.
The welfare implications of extreme fast-growth selection are severe and systemic. Lameness in broilers involves genuine pain — research using analgesic-preference tests demonstrates that lame birds choose pain-relieving food over normal food, confirming their motivation to seek pain relief. Cardiovascular failure affects birds at a population level. The genetic modification of broilers for growth rather than health is a fundamental welfare problem that cannot be resolved through environmental improvements alone.