Three times a day, Merle Mills races pigs around a 150-foot course he built beside a hay barn on his Poolesville farm. It's serious business, he says -- the pigs are in training for a run at the Montgomery County Fair, which ranks right up there with the White Flint Mall and the Kemper Open among the county's top attractions.

But for the porkers who sense food at the finish line, it is just a dash for the mash.

The truth is, admits Mills, 52, a plumber by trade who also raises animals, that pigs really don't care about athletic endeavors: "They just want to eat. You can say what you want -- I'm going to say they are professional racers -- but really they aren't running for anything but the food at the end."

Officials of the fair, which starts Aug. 19, have greater ambitions. They hope that the pig races being introduced this year for the first time will prove as popular as the traditional tractor pulls and 4-H contests.

State racing rules don't allow for parimutuel pig betting, but fair officials say five spectators will be asked to pick their favorites for each race, and whoever picks the winner will get a small souvenir. The pigs willing, Mills hopes to stage three races a day.

Pig racing began eight years ago in Galva, Ill., according to Roy Holding, head of advertising for Heinhold Hog Marketers there. The company, which brings about $7 million worth of hogs to market each year, was looking for a publicity gimmick to use at fairs and expositions.

Now the company spends about $100,000 a year training and showing its racing pigs, Holding said. He estimates that about 3 million people have seen them over the years.

At Mills' place one recent evening, five pigs-in-training, who hadn't eaten all day, leaped at the sound of a bell. They pounded around the first turn and found their stride on the far stretch. They dipped low to the inside rail and headed home, a cloud of dust and dirt behind them. And then, with a flurry of squeals and grunts, they crossed the finish line and dived snout-first into a waiting trough of hog mash.

Fair officials approached Mills about racing pigs after hearing about the sport last year at a convention of county fair officials in Las Vegas.

Mills said, " 'Why not? I'll give it a try,' " recalls Hazel Staley, fair secretary.

Mills, leaning against a board fence by the race course and almost yelling to be heard over the loud screaming of the hungry pigs ready to race, told the story a little differently. "I got beef cattle and pigs," he said. "So the bunch from over at the fair office, they went out to . . . a fair convention or something, and come back all wound up about it. There was nothing to do; I had to train them some pigs.

"They wanted me to say 'yes' right away. That was in January. But I didn't give them an answer, not until March . . . . I thought about it and I thought about it and I thought about it, and I said hell, it's a challenge. So I told them I'd give it a whirl. No, it's something you just don't jump off into, I tell you, to train a pig to race. I planned on everything being the worst, and it wasn't that bad, either."

His hog-rearing friends "thought I was crazy as hell," Mills said. "Half of them didn't believe me, and the other half thought I was crazy. . . . Nobody's laughing at me now."

To some, Mills' logistical concerns might seem laughable. Like, how would he keep the pigs' racing jackets on? And how does one keep more than five pigs from pushing their way out of the pen at starting time?

To solve the first problem, he fashioned clips from plastic piping and fastened colored felt blankets under the little pork bellies.

But his bigger problem was holding the eager porkers back. When he opens the gate of the pen to let the pigs down the fenced pathway to the starting gate, he must kneel down and throw his whole weight against them. When five pigs have struggled through his arms, he slams the gate closed and latches it.

Now, Mills must reduce his racing pigs from 29 to 25, so he can run five races with no pigs left over. "I'll pick out a couple that got too heavy on me," he said, as well as a couple that are "liable to come out of the starting gate and start rooting" around in the soil rather than running for the food.

The pigs, some of them females and some of them castrated males, were chosen from the piglets he had on hand. There are some Yorks (which are your basic white or pink pigs), reddish-brown Durocs, black with white-stripe Hampshires and black and white Spots.

"I really haven't clocked them, to pick out the fastest pig, because I'm not really interested in it," he said. "I don't even own a watch." A visitor clocked the faster pigs at 11 seconds or so, or about 9.44 miles an hour.

Mills, however, plans to keep on racing and is busy dreaming up new plans. He toyed with the idea of training spider monkeys as jockeys, he said, but was dissuaded by friends who persuaded him spider monkeys were too dumb to ride his pigs.

"If I had some more time, I'd train some of them for jumping," he said. "Steeplechase, you know. I think they'd jump . . . . With patience, you could teach a pig to do most anything.