There's a really good article on BloodHorse.com about how successful inbreeding to Secretariat has been. Here's the link: http://www.bloodhorse.com/horse-racing/ ... assing-fad
The article also has an interesting couple of paragraphs about the influence of one of the three foundation sires of Thoroughbreds, Herod. He has contributed some 17%-18% of the genes of modern Thoroughbreds, almost entirely through his daughters and their progeny. The article says that Secretariat's influence on the breed may be moving in a similar direction to that of Herod.