Comparing Sire Lines at the Highest Level

Comparing Sire Lines at the Highest Level

There is interest in comparing sire lines at the highest level in racing jurisdictions around the world. I have just completed an exercise for an American client in evaluating the sire lines in last week’s Kentucky Derby. Some of the world’s current leading sires are surprisingly absent.. To look at the issue further I decided to compare the top sires in America with those in Australia. I have not used the usual tools (average, earnings, winners per runner, stake earnings etc).

Keeping it very simple I have measured how many times a sire occurs in the pedigree. as the basis for this comparison. The data I have used comes from  two important races for 3yo as they are the top of the crop at the time they raced. The results will perhaps show what was important to breeders four years ago and perhaps also today. I have used the standard 5 generation pedigree (30 horses,15 on Sires side, 15 on the Dam’s side). The examination was not to find all the sire/broodmare lines, but look at which horses are contributing most to the pedigrees of the combined field. One can of course extrapolate from there.

Comparison of Sires in Kentucky Derby 2020 and Caulfield Guineas 2019.

I have chosen to compare the current sires whose progeny make up the fields in these two races. Both races are G1 races for horses of three years, of similar distance, worth approximately the same stake money. Exceptional winners of both races usually go on to be successful sires. They are also Races that owners would love to win.

Seattle Slew: a true champion in every way

The Kentucky Derby commenced in 1875.  In the last 50 years or so Secretariat (1973), Seattle Slew (1977), Sunday Silence (1989) and Unbridled (1990) have gone onto great things.

A P Indy: a son of Seattle Slew with 63 active sons at stud

The Caulfield Guineas commenced in 1881. It has also unearthed a string of talent. Luskin Star (1977), Redoute’s Choice (1999) Lohnro (2001), and Starspangledbanner (2009).

To have a position on the list a Sire has to be mentioned at least three times. The results are tabulated below:

What is interesting in the data?

Firstly, the stalwarts Mr Prospector and Northern Dancer maintain their powerful influence in both Countries.

  • The low showing of Danzig in America compared with Australia is surprising. No Danehill blood in the Derby begs many questions. One wouldn’t think quality would be one of those. Danehill was the broodmare sire of Frankel, considered by some (not by me) to be the world’s best horse ever. Danehill currently rates 83rd in Northern Hemisphere’s broodmare sire list. Perhaps there is something in that.
  • The Champions, Seattle Slew and A P Indy are well represented in the Derby but are noted to be largely absent in the Guineas.
  • The same could be said for Storm Bird and his son Storm Cat. The Storm Cat line is going well in America. Into Mischief, a great grandson of Storm Cat was America’s most sought-after sire in 2020. Storm Cat  has 92 active sons at stud.

Genetic Diversity

Horses in today’s thoroughbred population can trace their paternal linage to just three stallions. Similarly, more than 70% of thoroughbreds can trace their maternal linage to just 10 mares. Thus, there is little genetic diversity. Incorporation of the genes from some of the outstanding sires could provide that small change which separate success from failure in the breeding business.

Is Danehill Inbreeding a Pedigree Mistake

Is Danehill Inbreeding a Pedigree Mistake?

Danehill inbreeding has produced mixed results but is Danehill inbreeding a mistake? For sometime there has been much discussion that Danehill x Danehill would not increase the chances of producing black type horses. The matter appeared to be settled until Guelph (Danehill 2mx3f) won at G1 level. However, may I remind the resurgent believers of the old saying that given a typewriter (computer with Word 2016?), a monkey will eventually produce the entire works of Shakespeare.  I think the excellent work of John Boyce proves that Danehill inbreeding produces less SW than outcrossing..


What does the Data Show?

In the total thoroughbred racehorse population, about 2% will be black type winners. John took the data from 12,640 runners from 26 stallions who had at least 25 or more runners inbred to Danehill.

The percentage of runners achieving black type wins in this overall group was 4.9%. However, among these runners was 1,815 who carried at least one duplication to Danehill. The percentage of SW dropped to 3.2%.  This sample is significant in statistical terms. Inbreeding to Danehill produces less SW than outcrossing.

Danehill yearlings at MM National Sale August 2020

Though inbreeding to Danehill may not be a great choice, it still produces more SW than the average. There are two factors of influence when looking for a yearling inbred to Danehill.

  • The 3 x 3 cross has been the most productive. 3f x 3m has produced 25 SW with (5xG1,2xG2,8xG3,6xL). The 3m x 3m cross has produced 21SW, and 3m x 3f fourteen and its downhill from there.
  • A handful of sires have produced more SW through inbreeding, than outcrossing. Of these only Choisir is represented at this sale.
Can Pedigree Racing Index (PRI) help make a selection?

There are eight yearlings in the Sale that are inbred 3 x 3 to Danehill:

Lot No                              Pedigree                      RI score

1274    b f           Smart Missile-Myanma                 91.7

1371   bf f           Choisir-Watabout                          90.0

1484   br c          Teofilo-Feline Flye                      74.2

1642   b or br c  Your Song -Stage Performer         66.3

1674   b c          Hallowed Crown – Ailish                 65.0

1407   b c         Epaulette – Bantry House                64.2

1419  b f          Your Song -Breezing Home             59.4

1439  b f          Hallowed Crown -Darby’s Bid          59.2

The PRI scores show the Lots 1274 and 1371 have a good chance of being city winners  perhaps even going higher. The others will probably be struggling. Choisir has a better chance than most Danehill stallions to take advantage of inbreeding to Danehill so he would be worth a look. He is probably the fastest of the eight according to my Dosage evaluation.

PRI is a way of evaluation the sires side of the pedigree. To complete your evaluation you need to look at the dam’s side. And don’t forget the physical evaluation.