I’ve had absolutely no luck in breeding females from my original stock of T3 and T4 horses, sadly. I did breed my painted mare (whom I decided to keep on the basis of loving her looks), and got my first T5 stallion today, however. I don’t think he’s one of the fastest T5, and he’s certainly not the most attractive, but it’s my first T5 just the same!
I only have one last T3 mare from my original founder lines left, and if she can’t breed some more females, I’m going to be back out searching and taming wild horses to get my T3 stock back up again. Bummer.