Zenyatta is a perfect example on how that can work.
The thing is though, horse's like Zenyatta are few and far between. You know how it's been mentioned how 1 in every 20 horses bred will race? Well, of those 1's....probably 1 in every 1000 is a Zenyatta, regardless of what age they're raced from.
I've known horses here to race as 2 year olds, get 2 or 3 group 1 wins under their belt before they hit 3, only to continue til they're about 4 or 5.
I'm not advocating the racing of two year old horses. But while I believe they're too young, we also have to remember that this is the sport for which they were created. That while the *majority* of juvenile TB's can't cope with the workload and the stress, you do get the odd few who DO.
I think if Trainers were less under pressure from their owners, then you'd find that the balance of horses in training would be raced when they were READY, irrespective of what age the horse is.
TB's are genetically designed to mature a lot earlier than other breeds. I've put two year old TB's next to Warmbloods and Arabs of the same age, and there's just no comparason. In terms of mental and physical strength.
Of course, that's my own personal observation and belief.
I still stand by the fact that there NEEDS to be more control. A bit like how the - just for example - Warmblood breeders do it: Mares and Stallions are approved for breeding. As a rule, you can't just send any old mare to *that* particular stallion simply because he's very good and you think you're going to make a quick buck.
That's not to say that people don't. But there is a lot more quality control.
Centuries of refinement have gone into creating the most perfect specimin of athleticism. It's just unfortunate that human greed has to play such a huge role in the whole thing. (But isn't that always the way!?)