Longevity of a PRI Score

The Longevity of a PRI Score

A PRI score will change with time, but what is the longevity of a PRI score? Any process that involves statistical methods is only as good as the information in a data base. This particularly true when the data is continually changing. Any method using a data base must be robust enough to accommodate these changes. A data base which involves racehorses is continually changing. Just consider the AEI (Average Earning Index). Every run a horse has will change its AEI value. Similarly, every time a horse wins a Stakes Race, the pedigree compatibility factors will also change. The change will be almost imperceptible for a cross such as Northern Dancer x Mr Prospector. But what about the lesser lights?

Up Dated Results

To test the robustness my analysis system I re-examined the data entered in my first post of 2.5 years ago (Yearling Prices and Racing Ability: the rewards are hard to find). The updated results are given in the table below:

*PRI Score measured Feb 2019

**PRI Score measured Aug 2012

***PRI Band/Medium AEI is from Flavone Private data base. For example, Honesty Prevails with a PRI score of 93.8 lies in the data base band of PRI scores 95-90 which have a medium AEI value of $110k.


Firstly, as a prelude I need to state that the examination of seven horses is hardly statistically significant, but my conclusions are backed up by a considerable amount of data I have accumulated in over 20 years researching the subject. Secondly, breeding and/or finding good horses is an inexact science with a bit of art thrown in. For example, within PRI bands there is considerable variation in AEI values. However, I would predict that more likely than not the AEI figure is close to what you would expect from a horse with PRI values within that band.

  1. The PRI values measured for these horses in 2019 have not changed dramatically from those measured in 2021. The longevity of a PRI score held up well.
  2. In their racing career all these horses failed to return anywhere near their purchase price.
  3. The link between PRI score and AEI is reasonable for these seven horses. What was predicted is reasonably close to what was achieved.
  4. A phone call to me in 2019 would have saved some people a lot of money!


The Breeding Season 2021

The new breeding season for the Southern Hemisphere is underway. Most breeders have probably made their selection, but for those who haven’t read on. There are many books and web sources providing information on breeding thoroughbreds. I won’t expand on this here, but during the last few years I have covered a few breeding issues in my blogs. These issues are rarely canvassed by others but should be part of the selection mix.

Are Stallion Fees a Reliable Predictor of a Foal’s Prize-winning Potential?

This matter is covered in March 2021. The answer given by the scientific work of A J Wilson and A Rambaut (Biol Lett 2008, April 23 4(2) 173-175) is a definite no. You should not evaluate a stallion on his racetrack performance or that of his relations, but on its pedigree. Sometimes they are both good, but sometimes one is way ahead of the other. The real issue is how a stallion and mare’s pedigrees will fit together. These comments do not necessarily apply to those breeders whose aim is to make money using the formula best to the best and hope for the best. Someone will always pay big money for the progeny resulting from implementation of this plan.

Beware The Danehill Cross

A quote by John Boyce says it all “Top-Class racehorses inbred to Danehill have been conspicuous by their absence”. My limited investigation set out in August 2020, confirms this view.  Mares carrying Danehill or his son’s lines are now the preeminent pedigree lines in Australian mares. Crossing them to any Danehill line stallions requires a great deal of thought, investigation, and care. These Danehill problems spill over to some extent to the batch of Danehill family line stallions. In my view there are better options in the next breeding season for Danehill mares. The compatibility problems will decrease as the Danehill genes move to the right of the pedigree and become less important.

Don’t believe that Brothers and Sisters are the same

Octagonal: Mighty Racehorse, good Sire; full Brother Columbia only a good Sire

Quite often you hear or read that such and such is a good choice because its brother/sister was such a good horse. If such a conclusion is reached because of a deep pedigree analysis it may have come validity. However, I have already explained why full brothers are different and as for brother/sister? One is XY and the XX. How different can you get?

Be Philosophical about Disappointment

Finally, even with all the best preparation in the world, you must be prepared for disappointment.  Recently, never has there been a more striking example as this. Mount Fuji (Snitzel – Ichihara) was a $2.8m yearling. After a racing record of 4 starts and results of 0-1-1 $20,850 the horse sold at auction for $75,000. Why the fall from grace?

On my system it had a superb pedigree with a PRI score of 99.3. This puts it in multiple G1 status in my Library. No doubt all the pre-sale veterinary checks gave the yearling a clean bill of health. Which makes us look for things that are not easy if not impossible to measure. Every mammal has a biological, genetically controlled, clock. That’s why we age. But throughout life it can also regulate physiological factors such as arthritis, immune response, breathing controls and general health well-being.  There are also psychological factors at work. Perhaps he didn’t really want to be a racehorse? A herd animal, perhaps he didn’t want to be an Alpha?

Mount Fuji might now find his mark at the $75k level of competition. For the new owners I hope he does. For the old owners my commiserations. I would probably given you the same advice you followed. Remember there will soon be the results of the new breeding season to examine