Q & A -- Can the 'X-Factor' be Incorporated in TrueNicks Pedigrees?

Dale asks: I am a small breeder in NY, and have a limited barn of mares. I have been fascinated with the X-factor in the breeding process and wonder why the nick reports do not highlight the heart scores of those known. It also would be nice to see if a stud is a single copy and if a mare was a single of double copy. I recently had a race filly die, and her heart was weighed as part of the autopsy. She has also been identified as a double copy mare, along with her dam. So of course, I would like to breed the dam again, but only to a single copy stud.... Any thoughts on how to locate just those that fit my criteria?

 Alan's response: Thank you for the question.

Firstly, TrueNicks is designed to measure one specific element of the pedigree, the affinity between the sire line and the broodmare sire line. Although this is only one pedigree factor, it is one that lends itself to objective measurement, and where there is a measurable and statistically significant relationship between the nick rating and potential racing ability.

We may well broaden the scope of the program to give scores to other pedigree aspects, but I am not sure that the heart scores would be one of these (among other reasons, it may be proprietary information). Personally, I question the absolute validity of the X-factor theory. There does tend to be some relationship between the dam and heart output (rather than simple size -- it is possible to have large heart that is not as efficient as a smaller one), but those who study hearts tell me that they also see trends among sires in this respect.

I think that the hypothesis that there is a single mutated gene on the X-chromosome that significantly and positively determines heart performance and subsequent race performance is a bit of a stretch.

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