Breeders who sell thoroughbred yearlings have been collecting historically high prices for their merchandise this year, which should delight them all. But some of them are truly worried about what is happening to their industry.

"Everybody wants to breed horses nowadays; nobody really wants to race them," one of the sellers remarked at the Keeneland yearling auction last week. "That's got to be unhealthy."

The trend is unmistakable, because the only way horse owners can reasonably hope to make big money is to breed them. Wealthy buyers were willing to pay $3 million for yearling colts this summer, even though no race horse in history has earned anywhere near that amount, because they hoped the animals would repay the investment when they went to stud. This sort of thinking applies not only at this headline-making level, but on a much more modest level. My level, for example.

Before I went to Keeneland in an effort to purchase a yearling, I took a hard, dispassionate look at the dollars-and-cents aspects of the venture. If I bought a $20,000 colt, I could spend another $50,000 in training expenses to carry him through the end of his 3-year-old season. If the animal took one bad step, or if he proved to have no ability, I would be wiped out.

But if I bought a filly with a decent pedigree, I would have a commodity with built-in value. If she won the Kentucky Oaks, that would be wonderful, but if she could not run a step, I could either sell her as a prospective broodmare or else breed her. I might have a producing asset for 20 years, while depreciating her total cost over five years, which is the sort of investment that accountants dream about.

There was only one trouble with my plan to acquire a promising filly; everybody else at Keeneland had the same idea. Prices went through the clouds. Fillies with pedigree virtues that I thought were very subtle were regularly bringing $75,000, $100,000 and much more.

Meanwhile, nobody wanted colts with the same sort of bloodlines. A buyer might conclude, "This fellow won't be a champ but he'll make a good, useful race horse," but then calculate that it will cost $50 a day to keep him in training in New York, that the purses he might win wouldn't be large enough to make him a profitable investment, and that he would probably have no future salvage value at stud. That's why nobody wanted colts.

As the man in Kentucky said, this trend seems unhealthy, although it is hard to foresee all its implications. But one result of the relative profitability of breeding and unprofitability of racing is obvious. Good horses are disappearing from the track faster than ever.

Pleasant Colony emerged as a top race horse in April; he will be retired for a stud career in the next month or two. Fappiano may have been the most gifted thoroughbred in America, but he was campaigned so cautiously and sparingly that he never got to prove it; his owner wanted him only to compile a record that would look good when he went to stud.

In Europe, the tendency to keep good horses in mothballs is even more pronounced. Storm Bird, the champion 2-year-old of last season, ran one race as a 3-year-old and will now probably be retired to stud. Shergar, the continent's superhorse, ran one bad race recently, and so will probably be retired so he doesn't do any further damage to his reputation as a prospective stallion.

The practice of subjecting good race horses to challenges and risks has become as rare as bargain-priced fillies.