Modern broiler chicken breeds grow at rates that cause chronic health problems and suffering. Transitioning to slower-growing breeds is the most impactful single welfare improvement for the 70 billion broilers raised annually.
Fast-growing broiler welfare is fundamentally compromised by their genetic makeup. Birds bred to deposit muscle at extreme rates cannot support their own weight comfortably by the end of the growing period. Many spend increasing time lying on litter in their final weeks. Tibial dyschondroplasia — abnormal leg bone growth — causes painful lameness in a significant proportion. Ascites (fluid accumulation from heart failure) and sudden death syndrome (cardiac arrest) affect additional percentages. Slower-growing breeds have sufficient time for musculoskeletal development to match body weight, resulting in substantially lower leg, heart, and lung problems. The welfare improvement from switching to slower-growing breeds is dramatic and measurable — it is the single most impactful systemic change available for broiler welfare.