Evidence on the optimal timing for spay and neuter surgery has evolved significantly, with welfare implications for musculoskeletal health, cancer risk, and behavior.
The welfare implications of spay-neuter timing have become considerably more complex as research accumulates on developmental effects of sex hormones in dogs. The simple recommendation for early sterilization at six months was developed when population control was the primary concern and health effects were unstudied. Evidence now shows that sex hormones play important roles in musculoskeletal development, immune function, and cancer risk that vary by breed, sex, and individual. Welfare-centered decision-making requires breed-specific knowledge, individual assessment, and owner capacity to manage an intact dog responsibly. The goal is not to abandon surgical sterilization but to time and approach it optimally for individual welfare.