Barbaro's breakdown at the Preakness Stakes has kicked up the debate over whether something is making thoroughbreds more prone to injury.
Some industry experts blame trainers' obsession with speed over stamina and durability. Others say economics drive a tendency to breed horses for looks -- and big bucks in the sales ring -- rather than for the racetrack.
"Not only are our races shorter, but we're also looking for faster times. These horses are being trained harder than in the past. In the past, they just got the horses fit and they raced them."
Geoffrey Russell, director of sales at Keeneland Race Course in Lexington, Ky.
"I think we're breeding a faster horse, more speed-oriented," said Geoffrey Russell, the director of sales at Keeneland Race Course in Lexington, Ky., which each September holds the world's largest yearling sale.
Those who insist something is going on cite one indisputable fact: There has been no Triple Crown winner since Affirmed in 1978.
"Not only are our races shorter, but we're also looking for faster times," Russell said. "These horses are being trained harder than in the past. In the past, they just got the horses fit and they raced them."
Many believe the lure of million-dollar stud fees is taking horses off the track much earlier in their careers, making it hard to detect durability.
"They baby them," said Steve Cauthen, who rode Affirmed and now runs Dreamfield Farms in Verona, Ky. "Obviously, horses that have big stallion potential, they don't want to get him beat."
The average career for an elite racehorse, such as Barbaro -- or, in recent years, Smarty Jones and Afleet Alex -- is becoming shorter all the time. Smarty Jones ran only nine career races, Afleet Alex 12, and neither ran past his 3-year-old season.
By comparison, 1941 Triple Crown champion Whirlaway raced nine times as a 3-year-old after winning the Kentucky Derby, Preakness Stakes and Belmont Stakes. Secretariat, the 1973 Triple Crown winner, raced 12 times as a 3-year-old and had 21 career starts.
"I think we don't breed horses for distance any more, and the modern way of training horses is not to run them so closely," said Penny Chenery, who owned Secretariat.
"We're breeding a chemical horse. Nobody really knows the long-term effect of what those drugs will do. ... It's weakening the breed and it's dangerous."
Arthur Hancock, breeder of Kentucky Derby winners Gato del Sol and Fusaichi Pegasus and owner of Derby winner Sunday Silence
And there's little doubt that some horses are bred with an eye toward how they'll look in the sales ring or future breeding fees rather than their potential on the race track, Russell said.
"The thoroughbred market has become a commercial marketplace more than a racehorse marketplace," Russell said. "In the '80s we had stables that bred to race. They never thought about selling the horse. It's changed dramatically nowadays. The be-all end-all is to sell very well."
Arthur Hancock, who bred Kentucky Derby winners Gato del Sol and Fusaichi Pegasus and owned Derby winner Sunday Silence, said there's another factor at work: the use of legal drugs in thoroughbreds that race in the United States.
Veterinarians commonly administer drugs such as the anti-bleeding drug Salix, formerly called Lasix, and non-steroidal anti-inflammatory drugs such as phenylbutazone, commonly known as Bute, a pain reliever.
"We're breeding a chemical horse," said Hancock, who owns Stone Farm in Paris, Ky. "Nobody really knows the long-term effect of what those drugs will do. ... It's weakening the breed and it's dangerous."
Not everyone believes the horses are getting weaker.
"What has changed in recent years is everything but the horse," said Anne Peters, a bloodstock adviser at Three Chimneys Farm in Midway, Ky., where Barbaro's sire, Dynaformer, stands at stud.
She believes trainers from the 1970s -- the last golden era of thoroughbreds, which saw Triple Crown wins by Secretariat (1973), Seattle Slew (1977) and Affirmed -- learned under the "old-timey trainers" who worked in the industry during the 1930s, '40s and '50s.
"I don't think we have trainers learning the same techniques. If you weren't raised and schooled by an old-time horseman, you don't know those tricks."
Anne Peters, bloodstock adviser at Three Chimneys Farm in Midway, Ky.
"I don't think we have trainers learning the same techniques," Peters said. "If you weren't raised and schooled by an old-time horseman, you don't know those tricks."
For example, Chenery said that Secretariat used to gallop a sharp furlong on the Tuesday before every race but that nobody does that anymore.
But Barbaro, Peters said, by virtue of his genes, may simply have been a victim of that other factor that can doom a horse -- bad luck.