A related note, but not nearly as scientific. A book came out in the last year or two called Race Horse Breeding Theories that is a collection of articles by various authors. Rommy Faversham, who writes for the Thoroughbred Times, wrote a fascinating (at least to me) chapter about in-breeding to the female line, especially to certain foundation mares. He ran a number of analyses of mare in-breeding that produced a statistically significant increased number of stakes winners. It's not handy so I can't quote it, but I found the analysis pretty compelling. I used the method for choosing stallions for my mares this year, so in 2010 I'll let you know how well it worked.