Just as parents once kept idiot children out of view to avoid public disgrace, owners don't often put embassassing thoroughbreds on display.

Those many well-bred yearlings who cost astronomical sums and prove unable to run seldom wind up in claiming races where people can laugh at them. Somehow, they always disappear quietly, without a trace. For this reason, it was surprising to see the pedigee on a colt named Man Tan who was entered in a cheap claiming race at Gulfstream Park this week.

Man Tan is a son of Kentucky Derby-winner Bold Forbes and the mare Spaws Arrow, who previously produced the great filly Alma North. Pedigrees like this can command hundreds of thousands of dollars on today's booming bloodstock market. But trainer George Getz would be willing to sell this particular pedigree very cheaply.

Getz and his owners thought they had found a brilliant prospect when they say Man Tan at Hialeah's sale of 2-year-olds last March. They knew that a pedigree doesn't mean much if a horse doesn't have the confrontation, but Getz said, "He was beautifully made. And when he galloped: Geez! He looked good. He bowed his neck like a stakes horse."

When he went through the auction ring, Getz's owners were stunned to get this future champion for a bargain price of $60,000. It was one of those fluke prices that occur in horse sales occasionally, and other people reconized it almost as soon as the gravel had fallen. Another owner promptly offered the purchasers of Man Tan $100,000 for the colt; and instant $40,000 profit. They declined, and Getz took Man Tan back to Chicago to start training.

He learned immediately that the colt had one defect accompanying his wonderful bloodlines, conformation and way of galloping: he was slow. Still, the trainer was distressed. "When I started to breeze him," Getz said, "I thought anybody by Bold Forbes had to have a lot of speed, but this one didn't. So I thought he must be a horse who wants to go a distance, and there was no need to rush him."

But the owners were getting impatient and wanted to see Man Tan run, so Getz entered him in a sprint at Arltington Park, knowing he had no chance. "The people saw the breeding and bet him down to 3 to 2," he remembered. "One of the owners saw the odds and figured somebody must know something, so he went to bet."

The money on Man Tan did not prove to be smart money. The colt lost by 15 lengths. He ran twice more at Arlington during the summer, and in those three starts he beat a total of five horses. What he needed, Getz decided, was time to grow, develop and mature, since his future -- if any -- would be in distance racing. Man Tan was turned out on a farm for four months. When he came back, he was well-rested -- and just as slow as before.

The owners couldn't agree what to do with him. "Mr. (Milton) Friedman, who has some sense, wanted to run him for $5,000," Getz said. "Mr. (Philip) Teinowitz is still eying the Belmont. So we compromised.

Getz entered the colt in an $18,000 claiming race Tuesday, against ill-bred rivals who wouldn't have been permitted in the same sale with him a year earlier. He beat two horses, losing by 17 lengths, making one wonder just what has happened to mankind's efforts over the past two centuries to improve the breed.

It is, of course, not in the nature of horse owners to write off a $60,000 investment as a total loss. "He's a real strong healthy horse," Friedman noted. "Maybe he'll be better as a 4-year-old."

Getz was somewhat realistic. "I canbest describe this horse," he said, "as lacking both ability and courage."