Spay-neuter programs prevent overpopulation and reduce some disease risks, while current evidence supports more nuanced timing decisions.
Spay-neuter is one of the most significant welfare interventions at the population level — the dramatic reduction in shelter euthanasia over the past 50 years is substantially attributable to sterilization programs. At the individual level, the welfare calculation is more nuanced, particularly for large breed dogs. Emerging evidence suggests that hormones play important roles in musculoskeletal development, and early removal may increase risks of certain joint conditions. This does not argue against spay-neuter but suggests timing should be discussed with veterinarians on an individual basis. For cats, standard timing remains appropriate. For all species, preventing unwanted pregnancies through timely sterilization remains a clear welfare priority at the population level.