Kennel Club breed standards define physical traits in pedigree dogs, with growing pressure to reform standards that have produced animals with severe inherited health problems.
Selective breeding for conformation traits at the expense of health has created populations of dogs with chronic respiratory, orthopaedic, neurological, and skin problems. Bulldogs cannot give birth naturally in most cases. Cavalier King Charles Spaniels have skulls too small for their brains, causing painful syringomyelia. German shepherds with exaggerated hindquarter angulation develop early arthritis. Breed standard reform requires engagement with breed clubs resistant to change. Health test breeding requirements offer a mechanism to improve welfare within existing breeds.