Modern broiler chickens grow so rapidly that leg disorders causing chronic pain are among the most prevalent welfare problems in commercial poultry production, affecting hundreds of millions of birds annually.
Leg disorders in broiler chickens are among the most significant welfare problems in animal agriculture by scale. When one quarter of the 9 billion chickens raised annually in the US experience painful leg problems, the total suffering is enormous. The pain is real and measurable — lame chickens self-select analgesic medication when given the choice, demonstrating awareness of their own discomfort. This is a problem created entirely by human selective breeding decisions and can be substantially reduced by adopting slower-growing breeds, a change that the welfare science community has repeatedly recommended.