11/28/2002 1:00AM

Northern Dancer lineage is diluting


LEXINGTON, Ky. - The results of last weekend's most prestigious international races, the Grade 1 Hollywood Turf Cup and the Grade 1 Japan Cup, reinforced two principles of modern Thoroughbred breeding. First, Northern Dancer was the greatest source for premier international turf horses in the last century, and second, the preeminent families of breeding tend to produce the most consistent sires.

In the Hollywood Turf Cup, Sligo Bay, a son of the great Northern Dancer stallion Sadler's Wells, won the 1 1/2-mile race by a length in 2:27.22. In Japan, Falbrav, by Sadler's Wells's full brother Fairy King, was the narrow victor in the 1 1/2-mile race over the Lear Fan horse Sarafan.

Both Sadler's Wells and Fairy King are out of the Bold Reason mare Fairy Bridge. This is an exceptional family developed in America by the Hancock family at Claiborne Farm, for whom it produced champions Moccasin and Gamely. Fairy Bridge is out of the Forli mare Special and is a half-sister to Claiborne-bred Nureyev. This is an extraordinary family for producing sires, especially when bred to Northern Dancer.

Sadler's Wells, Fairy King, and Nureyev have sired numerous champions, classic winners, and top international competitors. They are three of the five or six best sons of Northern Dancer as stallions.

Yet, as important and successful as Northern Dancer and his best sons undoubtedly are, where is the breed going without their genetic guidance? Of his better sons, only Sadler's Wells (age 21), Be My Guest (28), Night Shift (22), Dixieland Band (22), and Danzig (25) are still active at stud. Since Nureyev, El Gran Senor, and Storm Bird only fairly recently died or left active service, the breeding world is not going to change overnight, but the great shift is coming.

When his last top sons leave breeding, Northern Dancer will be that much more removed from the annual genetic combinations of Thoroughbred matings, and his influence will be reduced by half. Whereas Northern Dancer himself was half of the genetic contribution to each of his offspring, when his sons and daughters bred on, Northern Dancer's influence was - on average - reduced by half.

In the random combinations of traits and qualities, some of Northern Dancer's "grandchildren" received more than their average share of his influence. Many others received less. And when this average share is halved again by transmission from his second-generation descendants, the result will be predictably weakened.

Some of his third-generation descendants, those offspring of Northern Dancer's grandsons and granddaughters, will have little relation to this tremendously important stallion. While on average, these descendants will have about a 12.5 percent contribution from Northern Dancer's genes, that number will vary considerably.

And how much difference will Northern Dancer make when he is only one of eight contributors to the gene pool, rather than contributing a half or a quarter?

That is the reason that male lines tend to die out in the span of three generations. The competition is too intense to retain them for sentimental reasons, and the genetic factors make it impossible to retain the influence of deceased sires as they move farther back in pedigrees.

Even as some breeding influences diminish, others increase. Northern Dancer's grandsons Storm Cat and Deputy Minister have led the general sire list and have produced sires who show promise of carrying on Northern Dancer's line, although stamped in the slightly different molds of Storm Cat's and Deputy Minister's own influences.

Sadler's Wells is showing little evidence that his sons will carry on his own preeminence in European racing, but some of his best sons are only beginning their stud careers. Already the leading sire in England and Ireland on a dozen occasions, Sadler's Wells is a steady influence for runners who improve with age and distance, typically liking 10 to 12 furlongs and showing their best form when there is a little give in the ground. As High Chaparral showed in his decisive victory in the Breeders' Cup Turf in at Arlington Park, the top offspring of Sadler's Wells are very high-class racers, and they can carry their form against the best international competition.

Group 1-placed at 2 and Grade 1-placed at 3, Sligo Bay had been knocking on the door at the highest level. Now he's in, and his success gives him some new opportunities as a stallion prospect. Sligo Bay is out of the Halo mare Angelic Song, a full sister to champions Devil's Bag and Glorious Song, as well as the good sire Saint Ballado.

They all were produced by the Herbager mare Ballade, and are all foals by Halo, who is also the sire of Sunday Silence and Kentucky Derby winner Sunny's Halo. Ballade has developed her own branch of this fine family, with her daughter Glorious Song producing champion Singspiel and the good stallion Rahy, sire of champion Serena's Song.