Mass spay-neuter programmes are the primary tool for reducing companion animal overpopulation, but access, effectiveness, and the welfare of the animals undergoing surgery all require attention.
Spay-neuter population control is a welfare intervention at two scales: the individual animals whose welfare is served by surgery (preventing reproductive cancers, pyometra, difficult births) and the population-level welfare of animals who would otherwise enter the shelter system. The surgery itself carries welfare costs -- anaesthesia risks, postoperative pain, recovery period -- that are outweighed by long-term welfare benefits for most animals in most contexts. Access inequity is the primary challenge: animals owned by lower-income families are less likely to be neutered, contributing to higher reproductive rates and shelter intake in these communities. Subsidised and mobile clinic programmes directly address this welfare disparity.