Uh, sports competitors almost always have great bodies. They get it from the exercise. Yes, that includes face too. And shaving yourself is not that much to do. Hell, they probably can get someone to do it for them.
But now back to cloned horses competing in normal races. Sure, but in the long run it will probably make every horse cloned to perfection. I mean, horse's penis can only grow so big it's better to clone the largest one and shove it in the back of the competitors owner. But will it make it more athlete like? No.