Modern broiler chickens have been selectively bred for rapid growth at rates that cause serious health problems, representing one of the most severe welfare crises in contemporary animal agriculture.
Broiler chicken genetics represents a case where selective breeding has produced animals whose normal functioning causes them chronic pain and early death from physiological failure. This is not the incidental consequence of poor management — it is the direct result of selecting a single trait (growth rate) at the expense of cardiovascular, skeletal, and respiratory system integrity. The scale is staggering: over 70 billion broilers are produced annually worldwide, and the majority live their final weeks in various degrees of pain from leg disorders. This is arguably the largest single source of animal suffering currently operating — and it is addressable through breed change alone.