Millions of dogs are euthanized every year, many of which come from unintended litters. The only way to prevent the birth of millions of unwanted dogs is to spay or neuter adults before they reach sexual maturity. Affordability and accessibility rank among the top 10 reasons owners give for not sterilizing their dogs. We’ve compiled lists of many low-cost spay/neuter clinics in Colorado, and more states are coming.