Horses aren't fully developed, too many injuries because they're racing too young at 3-yrs. That's my opinion and that could make this thread run 20 pages with all kinds of differing opinions.
3 years is fine IMHO, 2 year old is when they start and that is a bit young
Some changes in the dog (especially sight hound/racing dog) world too.
Couple of years back the thinking was if one figured out their male wasn't going to be a breeder/confirmation show dog, then they get clipped early. Our most recent one, Dandee, came with a contract said we wouldn't neuter him for 16 months minimum. He has some pretty well developed muscular legs, stockier than our other male who was clipped early. And we stayed away from performance type events with him until he was over a year.
Makes sense to me, look at the difference between a steer and an ox.
Imagine it's not a lot different with horses. Don't push them until they've fully developed and I guess that's where the controversy is? Big money players want some return on investment too???
