4 diff. rabbits vets here in Michigan recommend spay/neuter starting at 16 weeks of age. This way the hormones don't get the chance to "kick in", and more importantly, the bunnies don't really have a chance to develop bad habits..... Young rabbits also recover much quicker than older bunnies, plus it makes their urine smell less strong and calms them down dramatically, since their behavior is not hormone-driven. And, male buns can get reproductive cancers, just not nearly at the rate of the females.