Hi Rab,
I have only recently started to play SO5 on a serious basis (was previously just toying around to get used to it) so I haven't had a chance to breed any amazing horses as of yet, although I do have a great horse to get my breeding started
My aim is to breed the best horse I have to gain as many Colts/Fillies as I can. I will then continue breeding through those in the hope that the family tree strengthens while removing the weakened traits. This however will take many many seasons to achieve, and would assume this is a pre-requesite for all trainers if they wish to have horses of the standard that may compete adequately in the online league.
The trainers in the online league most likely have horses that were breed over the course of 20-50+ seasons, so that would give you an idea of the strengths of some of the horses you could be up against.
I was advised that the new Season starts in September, which is when new entries are acceptable, therefore like me you will have around 4 months of preparation
Best of luck and enjoy the game !
P.S. this link will help with exporting etc.. viewtopic.php?f=16&t=4866