Spay and neuter surgery reduces companion animal overpopulation, but timing and approach involve genuine welfare trade-offs that veterinary science is revisiting.
Spay-neuter programs have been central to companion animal population management and have prevented enormous amounts of suffering from overpopulation. However, the welfare picture is more nuanced than simple promotion of universal early surgery suggests. Research in large and giant breed dogs has documented elevated risks of orthopedic disease and some cancers following early gonadectomy, driven by the role of sex hormones in musculoskeletal development. Veterinary professional bodies are revising recommendations toward later timing for large breeds, sex-intact alternatives where behavioral management allows, and consideration of individual risk factors. The population welfare benefit of reduced unwanted animals must be weighed against the individual welfare costs of surgery risks, ideally through the availability of reversible contraceptive alternatives.