SAN FRANCISCO - Despite winning the 2003 Kentucky Derby and Preakness Stakes, Funny Cide could not make millions for his owners in stud fees. That’s because Funny Cide was castrated shortly after birth, so breeding was impossible.

But now there is an intriguing — if still remote — possibility of extending Funny Cide’s dead-end bloodline: through cloning.

“Obviously, it was a mistake that he was gelded in the first place,” said Funny Cide co-owner Jon Constance, an optician in Sacketts Harbor, N.Y. “If there’s a way to rectify that mistake, why wouldn’t we look into it?”

Constance said he and his nine co-owners, most of them high school buddies who paid a combined $75,000 for Funny Cide, have received “very preliminary inquiries” into cloning the champion, whose career earnings top $3 million.

After all, the colt Smarty Jones was sold for $39 million shortly after his Derby and Preakness victories last year and now fetches $100,000 for every offspring he fathers. Similar riches could await the owner of this year’s Derby winner, Giacomo, who will try to win the Preakness on Saturday.

But The Jockey Club, which monitors thoroughbred racing and breeding in North America, keeps an extremely tight rein on breeding practices. Only natural breeding methods are allowed, and club rules explicitly prohibit not only cloning but artificial insemination of any kind.

“We are trying to ensure the integrity of the breed,” said Bob Curran, a spokesman for The Jockey Club, which monitors some 35,000 births a year. The 111-year-old institution also is bent on preserving the sport’s competitive traditions.

Since 2001, The Jockey Club has required that horse breeders submit DNA proof that each foal was bred naturally. Such DNA testing easily could uncover a clone, because it would be an exact duplication of a single horse rather than a mixture of two parents.

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Last month, Texas A&M announced it had created the first cloned horse in the United States. The colt, dubbed Paris Texas, is the world’s third successfully cloned horse. Each of those efforts used hundreds of eggs to yield a single foal, since the kinds of techniques researchers developed years ago for other species are still being figured out for horses.

Texas A&M researcher Katrin Hinrichs and colleagues found success by tricking the cloned embryo to begin growing as if it was fertilized. She said she has a couple of mares now pregnant with new clones, and that her lab is becoming ever more efficient at the process.

Hinrichs doesn’t expect thoroughbred racing to soon embrace cloning, but believes the technology could help solve mysterious fertility problems such as the one that plagues the champion thoroughbred Cigar, who won a record $9.9 million during his career. Cigar retired to stud in 1997 and should have fetched $75,000 per foal fathered, but instead shot blanks. His owners had the foresight to take out a $25 million insurance policy protecting against infertility, but Cigar’s bloodline is done.