Understanding the Power of the X Factor: Patterns of Heart Score and Performance

Rating:
Summary: Still scratching my head
Review: After spending more than a week of trying to validate the information in Marianna Haun's latest book, I've come away less impressed by the whole X-factor theory than I was after reading the first book.

I think that there are some serious problems with Marianna's research, yet at the same time, she's onto something with merit. There is something to the whole idea of sex-linked performance traits, but I don't think that it's as important as Marianna makes it out to be, nor do I think that her research has been checked thoroughly enough to be very useful to thoroughbred breeders.

I found myself removing 5-10 double copy mares from her list just trying to get some of the pieces of the puzzle to fit together and always ending up with loose ends that couldn't be tied together. The end result is that it's probably not really possible to determine accurately from her theory if a specific horse is carrying the x-factor or will have it. Instead, the best one can probably do is to make sure that horses like War Admiral and Blue Larkspur appear in X-chromosome passing positions and hope for the best.