Seriously? Thoroughbred breeders are incredibly concerned about the lack of genetic diversity in the breed! Why do you think AI is not allowed and only live cover? That was mandated to limit the number of foals a stallion could sire per year and help prevent the overuse of popular stallions from further reducing the gene pool. The growing popularity of stallions standing part of the year in the Northern Hemisphere and part of the year in the Southern Hemisphere and thus breeding almost year around is a huge concern in the Jockey Club and may result in furture registration rules because it too is reducing the genetic diversity of the breed. Thoroughbreds have, thanks to their lack of genetic diversity, developed horrible immune systems. No matter how routinely she's been vaccinated, a Thoroughbred mares colostrum often isn't good enough - foals are routinely given plasma shortly after birth to ensure they receive immunity. I could go on and on but lets suffice to say that the Thoroughbred could be used as the poster breed for why a narrow gene pool is not a good thing!