I don't believe neutering a domestic animal "slows" them down, as it only takes away the mating instinct. That's all. It keeps them from running away to find a mate. I don't know why people think it changes behavior...it really doesn't. Especially if done when they are very young. Some people attribute all kinds of weird behavior things to "fixing" their pet, but it's not proven. It's usually the owner who acted differently after the neutering, and that's what's caused the behavior change in the pet.