The genetics of modern broiler chickens have been selected almost exclusively for growth rate, creating birds whose bodies grow faster than their legs and hearts can support.
Broiler chicken genetics represent a welfare emergency affecting tens of billions of animals annually. The selection for extreme growth rate has created birds that spend significant portions of their short lives in pain — unable to walk normally, sitting in litter to avoid bearing weight on damaged legs, suffering cardiovascular stress from hearts that cannot keep pace with muscle growth. The solution is known: slower-growing genetics, combined with better housing and enrichment, produce birds with substantially better welfare. Consumer pressure and corporate commitments are driving change, but implementation lags commitments significantly.