Trinity College, DublinTrinity College, DublinHuman taboos may be one reason why inbreeding within the first four generations or less has not always been practiced systematically with thoroughbreds.

There are others, of course, including a fear that instead of “fixing” desired traits and gaining double success you may get double trouble, either physically or temperamentally. This can involve lower reproductive efficiency, poor disease resistance and lack of size as well as hiding recessive genes that have negative potential.

Whether those fears have validity, providing the application of inbreeding is scientific and based on careful study of families, must be debatable and, for what it’s worth, any two modern thoroughbreds are pretty closely related whatever their immediate backgrounds.

Research led by Professor Patrick Cunningham of Trinity College, Dublin, a couple of years ago into more than 200 horse showed that Darley Arabian’s Y chromosome, which carries the male genes, is found in 95% of modern thoroughbred stallions.

Similarily, the mare Tregonwell’s Natural Barb contributed 14% of the genes passed down the female line. The research proved that any pair now shares 47% of its genes.

But what about closer doubling up?

Northern DancerNorthern Dancer (Kentucky Derby 1964)With sires, in particular thanks to the remarkable influence of Northern Dancer, there is a tendency for this to occur nowadays almost by default rather than as a conscious act. This is evident in the pedigrees of European Pattern winners, since over the last decade instances of inbreeding have increased two and a half times, reaching a total of 123 horses last year, 80 of whom had Northern Dancer twice in the first four generations.

Certain breeders sometimes make a deliberate pitch at concentrating Northern Dancer blood. Khalid Abdullah has tried it with notable success. One of his leading performers in the States, dual Pacific Classic winner Skimming, was inbred 2 x 3 to Northern Dancer. So was Viviana, successful in two Listed races and dam of Sightseek and Tates Creek, who notched nine Grade 1 races.

Another horseman who knows his stuff and tried the blend was Vincent O’Brien, whose good American chaser Trebizond was inbred 2 x 3 to Northern Dancer and 3 x 2 to the sisters Special and Lisadell. To what extent the ‘Northern Dancer effect’ benefited these horses is incalculable, but it might have been crucial and assuredly did them no harm.

TourbillonTourbillon ( back a little further, Marcel Boussac, the best-known exponent of inbreeding, used principally the sire Tourbillon and his family. He obtained Arc winner Coronation V (inbred 2 x 2 to Tourbillon, but temperamental and no good as a broodmare), while Frederic Tesio’s stakes winner Tanaka was inbred 2 x 2 to Tofanella.

Tanaka brings in the question of inbreeding to females, a more problematical arrangement given the vastly smaller numbers of foals any broodmare has compared with a stallion. Usually this has been done via stallion sons rather than mares on their own account in the bottom line. Breeders’ Cup Juvenile winner Stevie Wonderboy is inbred 3 x 3 to Weekend Surprise, via her sons A P Indy and Summer Squall. Even Lord Derby, with his inbreeding to dual Guinness winner Pilgrimage, did this through her sons Swynford and Loved One, getting Classic scorers Sansovino and Ferry, siblings inbred 3 x 3 to Pilgrimage. However, in the Tanaka vein, Equadif, dam of Arc runner-up Epervier Bleu, was inbred 2 x3 to Pretty Lady, including in the bottom line, while Danehill, bred by Khalid Abdullah, was inbred 3 x 3 to Northern Dancer’s dam Natalma. As a result, good current filly Peeping Fawn is inbred 4 x 4 x4 to Natalma.

Given that such as Tesio and O’Brien successfully had a crack at inbreeding to mares. It seems odd that so few current breeders make an effort to do this. Some could surely afford to experiment, given that they posses almost limitless resources to buy broodmares and use whichever stallion they choose.

With six daughters and two stallion sons, Grade 3 winner Weekend Surprise would be a candidate, as would Grade 1 winner and multiple Group/Grade 1 producer Fall Aspen *. For Khalid Abdullah, there will be possibilities with Hasili, the most successful broodmare of modern times. She is the dam of one successful stallion, Dansili, with another young sire, high-class Cacique, having just started out. Hasili is also the dam of three exceptional racemares in Banks Hill, Heat Haze and Intercontinental.

With Danehill the sire of all but one of these progeny, and the other by a second Danzig stallion, Green Desert, there will be chance of intelligent duplication somewhere.

It will be fascinating to see if the opportunity is grasped – and if so, what happens.

Courtesy of Thoroughbred Owner & Breeder August 2007

Fort WoodFort WoodWe have long been advocating the use of Fort Wood mares to Hobb Alwahtan, which provides inbreeding 3x3 to Fall Aspen.