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.