I think most vets recommend spaying before their first heat. That is when mine are usually spayed. Maude was a year old-but I was lucky, as she hadn't had her first heat yet-and I just couldn't get her done sooner I think most are done about 6/7 months-after that they are possibly going to go into a heat cycle-but each female is different, as for when they do. I, personally don't think it has anything to do with their "growing potential". That depends more on their genetics, and nutrition.