100 years of Epsom Derby data

By Sid Fernando

Just for the heck of it, I spent a portion of yesterday examining the pedigrees of the last 100 Epsom Derby winners. I wanted to tabulate the number of winners of the race that were inbred within five generations to a sire in tail-male descent by the sire line of the broodmare—exactly what I’d done with the Kentucky Derby in a previous post. What I found was that from 1910 to 2009, there were five Epsom Derby winners inbred sire line x broodmare sire line, or 5 of 100—5 percent. During this exact time frame, 4 of 100, or 4 percent, of Kentucky Derby winners were inbred sire line x broodmare sire line, too.

The last two Kentucky Derby winners, Mine That Bird (5×3 to Mr. Prospector) and Big Brown (3×3 to Northern Dancer), were inbred this particular way, but in England, surprisingly, the latest case of it occured with Erhaab (5×5 to Nearco), in 1994. Nearco, Mr.Prospector, and Northern Dancer were such prolific sires of sires and sire-line makers that it’s easy to see why they’d be prime candidates for sire line x broodmare sire line inbreeding. And in fact, of the five Epsom Derby winners inbred this way, four of them (4 of 5) were inbred to Nearco: Erhaab; Kahyasi (5×5) in 1988; Secreto (3×5) in 1984; and Roberto (4×4) in 1972. Before Roberto, there was no such inbreeding back to 1925 and Manna (5×4 to Bend Or).

None of this means anything other than what is factually stated—that 5 percent of Epsom Derby winners and 4 percent of Kentucky Derby winners over the past 100 years are inbred sire line x broodmare sire line—but a reader asked the other day whether some of this might be put in context, and I don’t really think it can.

However, I asked WTC’s Roger Lyons to provide some “meaningful” statistical data, and here’s what he gave me:

A) 12.2 percent of the 2009 Keeneland September yearling sale was inbred 5×5 or less sire line x broodmare sire line.

B) 13.5 percent of black type winners worldwide in 2009 were inbred same way at 5×5 or less.

At the time that the “large book” era arrived, which coincided with the advent of “shuttling,” sons and grandsons of Northern Dancer and Mr. Prospector were at the height of popularity. Large books and shuttling probably accelerated the incidence of inbreeding to these icons in general and by sire line x broodmare sire line in particular. With this in mind, that the last two Kentucky Derby winners are inbred to Mr. Prospector and Northern Dancer in this manner isn’t surprising. And I wouldn’t be surprised in the future if an Epsom Derby winner were to be inbred this way to Northern Dancer, either, because the combining of Sadler’s Wells through either Galileo or Montjeu—the two preeminent classic sires across the pond—with daughters of his paddock mate Danehill or his son Danehill Dancer would lead to 3×4 or 3×5 to Northern Dancer, and there are already at least 7 Group winners on this cross.

But the fact remains that historically to date the incidence of this manner of inbreeding has been rare in two of the greatest races in the world.

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