Selective breeding for exaggerated physical traits in many dog breeds causes severe, lifelong health problems that represent a significant and preventable welfare crisis.
Brachycephalic dogs breathe through airways permanently obstructed by their flattened skull structure. Many require surgery to survive comfortably — surgery that corrects an inherent structural deficit. Dogs with brachycephalic obstructive airway syndrome cannot exercise normally, pant effectively to cool themselves, or sleep without breathing disruption. Cavalier King Charles Spaniels with syringomyelia experience severe chronic pain from cerebrospinal fluid pressure on the spinal cord — a condition caused entirely by breeding for a skull shape too small for the brain it contains. These welfare problems are direct products of human aesthetic preferences imposed through selective breeding.