Modern fast-growing broiler breeds grow so rapidly that many develop painful musculoskeletal disorders, gait problems and organ failure before slaughter.
The current dominant broiler breeds have been selected almost exclusively for growth rate and feed conversion, with welfare treated as secondary. The result is a bird whose body outgrows its structural capacity. Chronic lameness means birds spend much of their time lying on wet litter, causing contact dermatitis. Slower-growing breeds add modest cost but substantially reduce suffering.