Commercial broiler breeding has optimised for growth rate and feed efficiency at the cost of significant welfare problems — leg disorders, cardiovascular disease, and metabolic dysfunction are embedded consequences of current genetic lines.
Fast-growing broilers are breeding failures in welfare terms — their skeletal and cardiovascular systems cannot support the extreme muscle growth that makes them commercially desirable. Femoral head necrosis, tibial dyschondroplasia, and angular limb deformities cause chronic lameness and pain throughout the birds' abbreviated lives. Ascites from cardiovascular failure causes progressive respiratory distress and fluid accumulation. The welfare cost is not incidental but is mechanistically linked to the selection pressure for maximum growth — selecting against it requires accepting lower growth rates and higher production costs.