Several Causes Cited in Racehorse Injuries : Survey: Longer seasons, more races and horses and harder tracks are mentioned by prominent racing people.

The injuries began in February, when top Kentucky Derby candidate Grand Canyon developed a knee problem that led to his retirement.

Cryptoclearance and Derby favorite Red Ransom were hurt soon after, and Champagneforashley two days before the Preakness. Next came Hawkster and Eastern Echo, who was Red Ransom’s stablemate. Sunday Silence and Easy Goer never made it to the $1-million Arlington Challenge Cup, which had been billed as the race of the year, because of injuries.

Classic Fame, Northern Wolf and Gorgeous also had their careers cut short by injuries.

And then came the Breeders’ Cup at Belmont Park on Saturday.

In the first race, Mr. Nickerson died of an apparent heart attack. Shaker Knit fell over him, and was humanely destroyed that night.

Two races later, heavily favored Go For Wand was leading Bayakoa by no more than a neck during the stretch of the Breeders’ Cup Distaff when her right foreleg snapped and she fell. The filly was humanely destroyed on the track, with a curtain set up to shield the scene from horrified spectators and millions watching on television.

It is unclear why so many famous racehorses have been hurt recently, but a survey of prominent racing people this week produced these theories:

Longer seasons and more races than before. Instead of the good horses being taken out of training for the winter and brought back to the races leisurely each spring, they continue to race until something goes wrong.

Thoroughbreds are bred for speed and competition. The good races provide the toughest tests. When the best race the best, as it was Saturday, they race their hardest until something gives. Go For Wand raced until she fell. That’s the nature of the sport.

With more racing coverage than ever, more attention is given to the careers of the top horses. More horses are being bred. There are more than 50,000 thoroughbreds foaled each year. Thirty years ago, there were about 5,000.

Hard tracks. Some people believe that some track superintendents are inclined to speed up their tracks when important races are coming up. When the speeded-up condition exists--the tracks are harder because there is less cushion--the fragile legs of racehorses can give way.

Seth Hancock, who runs Claiborne Farm in Paris, Ky., agreed with several of the theories.

“I believe there’s more injuries this year,” he said. “There’s so many more horses at so many more tracks. There used to be 5,000 horses born each year, and there was very little winter racing. It used to be that horses rested in South Carolina. They don’t rest now.”

Alex Harthill, a nationally known veterinarian, said: “They run all year. Around the race track, people say there’s two kinds of racehorses. One has problems, and the other will have problems.”

Trainer Hank Allen said he didn’t think the rash of injuries at Belmont was coincidental.

“It seems to me that tracks in many places get faster the closer the time comes for a big race.”

Joe King, superintendent of the tracks run by the New York Racing Assn., of which Belmont Park is one, said: “There’s no reason (for speeding up tracks). Our goal is uniformity and consistency. Nothing was changed for Breeders’ Cup week.”