when to neuter a dog
1 Once male pups are eight weeks old, it's likely that their testicles have fully descended, which is a necessary condition for performing the surgery. 2  According to the ASPCA, spaying and neutering can occur as early as eight weeks.easons for Early Neutering. Neutering dogs at an early age can actually keep some dogs from developing negative behavior patterns. Issues may include: 1  Aggressive behavior in some male dogs once they become sexually mature.