Rupert Cornwell: Big Brown win will not whitewash racing woe

Can glory expunge tragedy? Such is the question for American racing as it approaches the climax of its season, poised uncertainly between these twin extremes of sport and life.

Just four weeks ago, the filly Eight Belles had to be destroyed on the spot when, after finishing second in the Kentucky Derby, the first leg of the Triple Crown, she collapsed, shattering both front ankles. Inevitably, the dreadful incident brought back memories of Barbaro, who in 2006 sustained a similar, ultimately fatal injury in the Preakness Stakes, the second leg of the crown.

Now redemption, of a kind, is at hand. If he wins next Saturday's Belmont Stakes, a handsome deep bay colt named Big Brown – conqueror of Eight Belles in the Derby – will become the 12th horse in history and the first in three decades to carry off the greatest prize of all. Never has there been so long a period between Triple Crown champions, and never has the beleaguered sport needed a champion as much.

It will not be easy. Happily, a small crack in Big Brown's left front hoof appears to be healing, but then there is the curse of recent history. Big Brown is the seventh horse in the last dozen years to have won the Derby and the Preakness. But each of the previous six failed to win the Belmont.

This time potential nemesis awaits in the shape of the Japanese-bred Casino Drive. Big Brown will start odds-on favourite. But his challenger is undefeated, bred for the mile-and-a-half distance, and ridden by Edgar Prado, a Hall of Fame-bound jockey who has been a Triple Crown party pooper at Belmont twice, in 2002 and 2004.

There is, however, a third and most ominous reason for concern that lies not in the stars, but in the genes. The deaths of Barbaro and Eight Belles have created a crisis for American racing. Ever more loudly, animal rights groups claim the sport is too dangerous. The tracks are too unyielding, they say, the blue-riband races are held too close together, and horses are bred for speed at the expense of endurance.

The first two complaints do not bear serious scrutiny: the Triple Crown has always been run on the present tracks and calendar. The third, however, is if anything an understatement. American horse racing, quite literally, risks breeding itself to death.

All 20 starters in the Kentucky Derby were descendants of Native Dancer, a star thoroughbred of half a century ago. Some, including Eight Belles, have him in their blood line on the sire and dam side, and in multiple generations. Native Dancer's DNA is so prized because it carries marvellous speed. Alas, it also bears a weakness, a lack of durability and soundness – not least in the ankles.

As Bill Nack, a veteran of Sports Illustrated and ESPN who has spent half his life around horse racing, bluntly puts it: "The thoroughbred is now so suffused with the precious blood of Native Dancer ... so shot through with distant offspring who carry the markers of his tribe ... that today it threatens the viability of the entire breed."

Thus you have a genetic weakening of the breed, exacerbated by the use of steroids and other drugs to keep these overperforming but weakened and softened animals on the track. Stir in the refusal of the US Jockey Club to permit the adulteration of the thoroughbred strain with stronger outside blood and a financially driven, win-at-all-costs culture, and you have a recipe for deep, deep trouble – in Nack's words, "an equine world driven by speed, greed and the soulless dictates of the marketplace".

Racing may be a multi-billion dollar industry, but as a sport it is in a perilous downward spiral. Fragile horses mean more accidents, fewer appearances and thus fewer opportunities for horses to become stars, gaining a true national following.

Everyone has heard of Seabiscuit, victor over the Triple Crown winner War Admiral in 1938 in arguably the most famous match race in history. He raced no fewer than 89 times. The 1948 Triple Crown winner Citation ran 45 times and retired as a six-year-old. Even Affirmed, the last horse to perform the feat, in 1978, competed as a four-year-old.

Big Brown, however, may never race again after Belmont. After a mere six starts he will vanish from view for ever, to stand as a stallion under a deal that may net his owners $50m (£25.4m). Small wonder that it now takes an accident to jolt racing into the public consciousness.

Nonetheless, and for all his worries about the sport he loves, Nack is rooting for Big Brown: "The racing gods have decreed that only when he wins all three does a horse truly have what it takes. If Big Brown wins, he belongs."

In terms of blood-line, of course, he already does.

Brian Viner is away