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Of Math and Men (and Horses), part I

In my previous post, I described how my first employment in pedigree research came as a result of querying the validity of some sire line crosses published in an English magazine. Since then, I have harbored the ambition to create a better way of reflecting the success-or otherwise-of sire line crosses.

It's clear that attempting this with a limited database of stakes winners, as some do, is a flawed approach.

Seeking a more refined approach to a complicated issue, it became clear that being restricted to an archaic system comprised of a limited database of stakes winners would not result in a superior system-that would be starting with an inherently flawed premise. In fairness, I will say that these systems did the industry a fine service by demonstrating that sire line/broodmare sire line crosses do have a correlation with success. Unfortunately, while they do a reasonable job of reflecting broad trends, they are often yield misleading results with regard to specific matings. By treating all stakes winners as one universal herd-where, in theory, any sire in that universe can be mated to any mare-such systems measure only hypothetical, not real, opportunity.

In a situation where a cross becomes a very popular one, the figures can go badly out of whack. One example that comes to mind is that of Kingmambo with mares by Sadler's Wells, a subject I'll address in a coming post.

Creating a figure based on proportional representation within the population of The Jockey Club database would merely perpetuate the problem with a bigger group of horses. We determined that the TrueNicks system had to be created on the basis of real opportunity, and determined on the basis of matings which had actually taken place.

Putting this concept into practice was easier said than done. Assuming a large sample size, it isn't too difficult to determine whether the cross of a sire line with a broodmare sire line is doing better than opportunity. Of course, the cross can look very different depending on whether one examines it from the perspective of the sire or broodmare sire; both have to be taken into account. The Kingmambo/Sadler's Wells cross was, at one stage, a perfect example of that, improving Kingmambo and impairing the Sadler's Wells mares. Separate calculations yielded a Sireline Improvement Index (SII) and a Broodmare Sireline Improvement Index (BSII), tools which will ultimately be very helpful to breeders.

Click here to read part II

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