More rapid, more fragile

Modern broiler and turkey genotypes have been subjected to intensive genetic selection for body weight gain. This selection has resulted in major changes in the anatomy and physiology of birds. The incidence of leg abnormalities, lameness, twisted legs (valgus-varus angulation), tibial dyschondroplasia, and crooked toes is increased with fast-growing chickens. Rapid bone deposition is associated with decreased mineralisation, more porous cortical bone, and altered biomechanical properties.

Infectious disease such as Bacterial Chondronecrosis with Osteomyelitis (BCO) is associated with rapid growth and osteochondrosis. Bacterial infection and necrosis develop in rapidly growing bones (femora and tibiae) that are subjected to repeated mechanical stress, with structurally immature cartilage.