Commercial broiler chickens have been selectively bred to grow so rapidly that their hearts lungs and legs cannot keep pace, causing endemic health problems.
The selective breeding of broiler chickens for maximum growth rate has created an animal whose body is fundamentally incompatible with normal locomotion and physiological function. Leg disorders cause chronic pain that prevents birds from accessing food and water normally. Cardiovascular failure is routine rather than exceptional. These welfare problems are not aberrations but are inherent in the genetics that define modern commercial poultry production.