Modern broiler chickens have been selectively bred for such rapid growth that many suffer cardiovascular failure, leg disorders, and chronic pain simply from the strain of their own bodies.
The welfare crisis in broiler chicken production is perhaps the most numerically significant in all of animal agriculture. Billions of birds experience chronic pain from leg disorders caused by their bodies growing faster than their skeletal systems can support. Many cannot walk without difficulty; some cannot reach food and water. Cardiovascular disease kills millions of birds acutely. The density of conventional broiler housing - often 19-20 birds per square meter - prevents normal behavior and contributes to respiratory disease, footpad dermatitis from wet litter, and breast blisters from contact with soiled bedding. This suffering affects more individual animals than any other form of livestock production.