Brain International | Princequillo
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Princequillo makes an interesting subject given the unprecedented hype to which he has been subjected recently in efforts to support speculative theories relating both to “large hearts” and to what has been termed the “maternal damsire effect”. The role of Princequillo as damsire of Secretariat is central to both of these theories, and this appears to have been exaggerated beyond all proportion.


The facts

A short look at the facts can place the situation in perspective. The “maternal damsire effect” relies heavily on the myth that a number of stallions, including Princequillo, failed as stallions but were highly successful sires of broodmares. The theory explains this so-called phenomenon by postulating that certain genes skip a generation within the pedigree of a stallion in his capacity as a sire of broodmares, while lying dormant within the pedigree of the same ancestor in his capacity as a stallion. The main problem with this theory is that those propounding it appear not to have questioned the old-wives’ tale that some stallions are more effective as stallions than as sires of broodmares.

In almost all cases this is a complete myth. Princequillo represents perhaps the best example of all of this fallacy. He was in fact a highly successful stallion producing 13% black type winners to foals of racing age (as compared with a current figure of 12% for the highly promoted Storm Cat). Amongst others he sired Round Table, arguably one of the fastest racehorses ever, and amongst his other claims to fame as a stallion we can include Hill Prince, Dedicate, Misty Morn, Quill, Rose Bower and Prince John.

Princequillo as a sire of broodmares

As a broodmare sire Princequillo was responsible for 168 black type winners from 1,422 starters, or 12%. As with most other highly successful broodmare sires, Princequillo was little different from any of them in that they can all be shown to be marginally more successful as stallions. So much for the “maternal damsire effect”.

The proposition that Secretariat derived his superior capabilities from the fact that Princequillo was his broodmare sire and contributed his “large heart gene” through his X chromosome, appears equally misleading. The pedigrees of stallions currently registered in The Blood Horse Stallion Register make a representative yardstick for excellence, and provide ample statistics to demonstrate the role of Princequillo in a modern day pedigrees. To summarise our findings, taking a sample of the first 320 stallions listed alphabetically in the current edition of The Blood Horse Stallion Register, we find that of the 10,000 or so male ancestors within their pedigrees, Princequillo is present a little over 150 times.

For Princequillo to be in a position in the pedigree to supply the X chromosome, we find that such criteria are met in only 40 of these cases (0.4% of all male ancestors present). In terms of the influence of Princequillo, in the event that he were able to offer “large heart” genes, Princequillo’ s presence through sirelines, where he could have no capability of passing on the X chromosome, is 4 times greater than in the position where he might support the “large heart” theory. What is more, in these latter cases (where he could have capability of passing on the X chromosome) it is noticeable that these are mostly sires at the lower end of the stallions spectrum, and indeed many were at the lower end of the scale in terms of their performance on the racetrack. In the unlikely event that Princequillo had the power to pass on such special attributes, he appears to have made a pretty good mess of it!

The statistics just do not support either of the theories investigated above. A more likely explanation of what made Secretariat such a phenomenal racehorse will be explored in an article on Nasrullah to appear shortly in these pages.