Spay and neuter programs reduce shelter euthanasia and unwanted animals, but the timing and scope of these procedures involves welfare tradeoffs that science continues to refine.
Spay and neuter have transformed companion animal population management in high-income countries, dramatically reducing shelter euthanasia. However, the welfare calculus is more nuanced than it once appeared. In large-breed dogs, early gonadectomy is associated with increased risks of joint disease, some cancers, and urinary incontinence. Evidence-based recommendations increasingly favor delaying spay and neuter in large breeds to allow hormonal development. The welfare tradeoff between individual health risks and population-level euthanasia reduction is real, and recommendations are evolving as research matures.