Spaying and neutering companion animals prevents overpopulation and associated welfare harms, but optimal timing and the decision itself involves welfare trade-offs that vary by species, breed, and individual circumstances.
The welfare case for spaying and neutering companion animals is primarily rooted in overpopulation prevention. Millions of cats and dogs are euthanized annually in shelters because more animals are born than can be rehomed. Female cats in persistent estrus experience significant hormonal discomfort and the physical cost of repeated pregnancies and lactation. Intact male cats suffer injuries from territorial fighting and are at high risk of FIV transmission through bite wounds. The surgical procedure itself has short-term welfare costs but long-term benefits that substantially outweigh them for most animals. Individual trade-offs around timing and procedure type should be discussed with a vet familiar with current evidence.