Mahubah's Corner: Sibling Rivalry

Few debuts of an unraced maiden have drawn as much attention as Nicanor’s first start January 31. The race proved anticlimactic, as the full brother to the late 2006 Kentucky Derby Presented by Yum! Brands (gr. I) winner Barbaro grabbed a quarter coming out of the starting gate and finished 10th of 12 runners.

Nicanor obviously had an excuse for his performance, and only time will tell if he has some measure of his older brother’s talent. But is there reason to believe that the talent is there? How often do siblings come even close to measuring up to a top horse’s talents?

Anecdotal evidence is rich on both sides. For instance, the mare Perdita (GB) produced four colts to the cover of St. Simon. Sandringham did little and was imported to the United States, where his stud record is said to have led to John Madden’s observation, “Once you have found that a horse is no good, his relatives don’t help him much.” But Florizel II (GB), the eldest of the quartet, won the 1895 Goodwood Cup, and his brothers Persimmon (GB) and Diamond Jubilee (GB) were still better. The former won the 1896 Derby and St. Leger Stakes before leading the English general sire list four times, while the latter won the English Triple Crown in 1900 and was a four-time leading sire in Argentina.

The Lord Derby-bred mare Scapa Flow (GB) also had a remarkable series of successes with one sire, Phalaris (GB), producing 1928 St. Leger winner and four-time leading sire Fairway (GB); 1930 One Thousand Guineas winner Fair Isle (GB), and 1924 Champion Stakes winner Pharos (GB), a leading sire in both England and France and ancestor of the Nasrullah and Northern Dancer male lines in all their various branches.

On this side of the Atlantic, Blue Delight threw four stakes winners from four foals by Bull Lea, including 1952 champion 3-year-old filly Real Delight and 1953 Kentucky Oaks winner Bubbley. (For good measure, she also produced 1956 Kentucky Oaks winner Princess Turia to the cover of Heliopolis.) La Troienne produced three high-class stakes winners from three foals by Black Toney in champions Black Helen and Bimelech and 1938 Selima Stakes winner Big Hurry, compared to two stakes winners from 11 foals by other sires.

On the other hand, 1937 Triple Crown winner War Admiral had five full sisters that managed to win just one race between them. Native Dancer also had five full siblings, of which only one was a winner. Citation had full three siblings, of which one won. The list of high-profile failures that were full siblings to a top horse is long and seemingly endless.

In truth, of course, the odds are stacked against a good runner being duplicated by a sibling. On average, full siblings share just 50% of their genes, meaning that siblings can vary widely in genetic potential even in an average mating. (And, of course, siblings sometimes share substantially less than 50% of their genetic material thanks to the whims of chance.) Add to this the fact that most experts consider racing ability to be about 40-50% genetic with the rest dependent on environmental factors – training, nutrition, general handling, early experiences, and so on – and it’s easy to see why more full siblings to good horses fail than make names for themselves.

Still, common sense would indicate that full siblings to a good horse have a better chance of being good runners themselves than half-siblings, all other factors being equal and the respective sires being of roughly equal merit. As a test of this hypothesis, consider the produce records of the dams of Eclipse Award winners in the male and female juvenile, male and female 3-year-old, and male and female 4-year-old-and-up divisions. While this is not a random sample of the Thoroughbred population by any means, or even a random sample of all good runners, the resulting pool of horses may still yield some useful information.

Collectively, the dams of the 199 champions studied were an outstanding bunch of broodmares. Between them, they produced 1,630 named foals of racing age through the end of 2007, of which 931 (57.1%) were winners, 198 (12.1%) were stakes winners, and 117 (7.2%) were graded stakes winners – excellent figures considering that in the breed at large, only about three percent of named foals ever win stakes and less than one percent become graded stakes winners. The percentage of winners would doubtless be still higher were it not for owners’ tendency to retire untalented sisters and half-sisters to good horses to the breeding shed after just a few races rather than drop them into the claiming ranks where they might have a realistic chance to win.

Of the champions studied, 82 had no full brothers or sisters; the remaining 117 champs had 233 full siblings among them. By contrast, there were 1,397 half-siblings to champions in the studied group. But if these results are any indication, perhaps breeders should have tried repeat matings more often. Of the half-siblings, 787 (56.3%) won, 165 (11.8%) became stakes winners, and 84 (6.0%) became graded stakes winners as of December 31, 2007 – not bad. The full siblings, however, yielded 144 winners (61.8%), 53 stakes winners (22.7%), and 33 graded stakes winners (14.2%). Only one champion, Glorious Song, numbered another champion (Devil’s Bag) among her full siblings, but still, the collective record of the full siblings cannot be called anything less than outstanding.

The proverbial lightning seldom strikes twice, and the odds that a truly great horse will be duplicated in a sibling are slim even under the best of circumstances. But at least from this preliminary look at the evidence, repeating a successful mating is a good way of substantially improving the odds of getting a good horse, and that’s all any breeder can reasonably ask.