Modern broiler chickens have been selectively bred for extreme growth rates that cause widespread chronic health problems, making growth-related welfare one of the most significant farm animal welfare issues globally.
The genetics of modern broiler chickens prioritize growth above all else, with predictable consequences for health. Bones, hearts, and lungs cannot keep pace with muscle growth, leading to endemic lameness, cardiovascular disease, and ascites. Lame birds suffer continuous pain and are unable to access food and water normally. Transitioning to slower-growing breeds does not eliminate welfare problems but substantially reduces their prevalence and severity.