Selective breeding of broiler chickens for rapid breast muscle growth has created muscle diseases including wooden breast and white striping that indicate welfare compromise in living birds.
Broiler myopathy is the clearest visual evidence that modern fast-growing chicken breeds are experiencing physiological stress detectable in their muscle tissue. When up to 80% of birds have pathological changes in their breast muscles, this is not a minor production anomaly but a sign that the genetic selection for rapid growth has exceeded the animal's physiological capacity for healthy development. Birds with severe wooden breast disorder have difficulty moving and spend more time lying in litter - behavioral evidence of physical compromise. The conditions cannot be managed away while maintaining extreme growth rates. Meaningful welfare improvement requires adopting slower-growing breeds, which several major European retailers have now committed to.