James Willoughby: 'Do Sires Pass On Synthetic-Track Ability?'

IT is fairly well accepted on both sides of the Atlantic that there are dirt sires and there are turf sires. According to received wisdom, the identity of a horse's sire provides a likelihood that it will be more effective on dirt or turf. Sadler's Wells, for instance, was regarded as a sire of predominately turf runners and A. P. Indy of dirt runners.

Assuming some genetic potential for this tendency really exists, we might ask if there is such a thing as a Polytrack sire; in other words, controlling for all other variables as best we can, is there something in the genotype of a horse inherited through the male line which makes it more suited to synthetic tracks than turf?

This question is particularly apposite for owners, trainers and punters in Britain and Ireland at this time of year. All-weather racing is proliferating, and the all-weather tracks at Kempton, Lingfield, Wolverhampton, Chelmsford and Dundalk all feature surfaces from the Polytrack family (also known as synthetics).

So, does a horse's sire give you strong information about whether to keep it going during the winter, rest it or sell it?

The difficulty in answering this question lies in the difference between scientific experimentation and statistical inference.

Say if you were researching the effectiveness of a new drug. You could select half of your test subjects as the treatment group and half as the control group. So long as there were no systematic differences between the characteristics of people in one group and the other, you could observe the difference in outcomes between patients who got the drug and those who did not and draw a safe conclusion about its effectiveness.

Unfortunately, manipulating the variables and forming an understanding of cause and effect is not possible for the horse racing statistician. To determine whether there are turf sires and synthetic sires involves making inferences from groups who have biased characteristics. Galileo's runners on the all-weather, for example, are a group of horses with significant differences from his turf runners. Principally, they are not so good. You don't spend multiple hundreds of thousands on covering fees or auction prices and aim a Galileo at the all-weather.

Failing to account for this pitfall when making comparisons between groups is called selection bias. In this case, what we could do to offset selection bias is throw every horse out of the sample who hasn't run at least once on turf AND at least once on Polytrack, and compare the performance of these runners across the two surfaces by sire.

Using data from British and Irish Flat racing from the last 10 years, and sires with at least 500 qualifying runners on turf and on the Polytrack family of surfaces, Figure 1 (click here) shows a plot of strike-rate on the polytrack family of surfaces (along the x-axis) and strike-rate on turf (along the Y-axis). Each point is a sire.

The main features of the graph are as follows:

–Strike-rates on Polytrack are generally higher than on turf, especially among quality sires. All-weather racing is less competitive than turf and opportunities are much richer to place horses to advantage. All-weather maidens are also commonly used now for backward 2-year-olds who return to the turf at three. Field-sizes can often be smaller;

–There is only a weak relationship between turf strike-rate and polytrack strike-rate, denoted by the shallow trend line and the wide dispersal of points;

–Halfway along each x-axis, the points are more widely spread than at either end of the axis (this is known in statistics by the wonderful term heteroscedasticity). There is more variance between expected strike-rate on turf and Polytrack for middle-ranking sires than for sires who are either exceptional or moderate overall.

–Some interesting points are picked out. Shamardal has a 19.9% strike-rate on Polytrack and a 11.6% strike-rate on turf among qualified runners, but the point representing him lies on the trendline because this is the expected difference between strike-rates on the two surfaces for good sires. By contrast, the point representing Dubawi is well above the line, indicating his runners are more effective on turf.

—Dutch Art has a higher turf strike-rate than expected from his Polytrack strike-rate. In general, his runners are better suited to turf. By contrast, Bushranger shows the opposite pattern. His runners have a higher strike-rate on polytrack than could be expected from their turf exploits.

In summary:

Sires with a higher strike-rate on turf than expected from polytrack include: Dutch Art, Dubawi, Motivator, Montjeu, Teofilo, Halling, Rock of Gibraltar and Azamour;

Sires with a higher strike-rate on Polytrack than expected from turf include: Bushranger, Exceed And Excel, Elusive City, Medicean, Kheleyf, Tagula, Intikhab and Bertolini.

Membership of one group does not exclude a sire from proficiency in the other, however. Moreover, there are no strong trends between the sire-lines from which sires descend.

Despite this, the record of sires on turf and Polytrack is so skewed–even when allowing for the noise inherent in measuring strike-rate–to believe it really likely there is a greater propensity among some sires to get horses suited to the Polytrack family of surfaces. –By James Willoughby