Robert and William Massey have become experts at breeding an animal many people have never heard of -- but someday may eat for dinner.

On their Fauquier County farm, the Massey brothers are raising a herd of about 30 beefalo, including some judged to be among the finest in the country. The beefalo, a cross between a cow and a buffalo, is more than a genetic curiosity; its advocates say it may one day help feed a hungry world.

The Masseys aren't alone. Dennis McCarty, another breeder, keeps a similar-sized herd nearby. Jay and Pat Hersch, Reston residents, are raising about 60 beefalo on a farm in Highland County.

In fact, although some still scoff a bit at the idea, the Masseys and others think the beefalo is an animal whose time has come. Farmers all over the United States are getting into raising beefalo, although not yet in numbers large enough to have an impact on the food market.

The beefalo has some advantages over traditional beef cattle. It tastes like beef, but tests show it to have higher protein content, fewer calories and less cholesterol. It can be raised to slaughter size sooner. Most important, it can be raised on only grass -- a boon to farmers who want to cut down on the use of costly feed grains.

There is still another advantage. A beefalo cow can bear a calf at 25 years of age, while the average bovine cow's fertility runs from eight to 12 years. A calf-bearing cow with double productivity is a breeder's delight.

"This very well could be the meat of the future," said George E. O'Connor, executive director of the American Beefalo Association, based in Louisville. "But we don't want to oversell the product. We want to be certain of the claims we can make for the beefalo. But with the country developing a taste for leaner meats, we feel there is definitely a place for the beefalo."

That is the message the beefalo fraternity is trying to convey. There are now several breeders' organizations and they make a big deal of annual shows, where prizes are awarded to top animals and breeders.

The Masseys last year not only won the American Beefalo Association's premier-breeder title, but also had the grand champion female, the reserve champion female and the reserve bull in the association's judging -- a record akin to winning football's Super Bowl. Their interest is in breeding -- providing the seed stock for others' herds -- because they envision big things for the beefalo.

"We got into this almost by chance, through an article I read in early 1976," said Robert Massey, executive of a small metals firm in Richmond. "Our goal is to have a purebred herd of about 50 beefalo cows, with an emphasis on breeding stock.

"My original interest came from my concern about how we would feed a growing world population," he said. "If you could breed a high-protein meat using less grain, this would be an important development. . . . There is a future in beefalo, and anybody raising livestock can see the favorable economics of it."

Beefalo advocates occasionally have had to endure more than amused grins and arched eyebrows from the skeptics. Henry A. Hilbinger discovered this when teen-age boys spray-painted that naughty "s" word across the haunches of his cherished beefalo.

That was a few years ago, when Hilbinger was showing his beefalo at fairs around Maryland and not getting much more of a rise from the curious than an occasional blast of spray-painted profanity on his stock.

Hilbinger got over the hurt, and he never stopped pushing the cause of the beefalo. He does this from his home in Woodbine, Md., north of Washington, where he keeps a supply of frozen semen he sells for breeding.

Hilbinger's pride and joy, a small herd jointly kept with Cyril Witte at his nearby Mount Airy farm, shares pasture with other, more conventional, livestock. Hilbinger thinks his beefalo embody a kind of salvation for a hungry world, if enough breeders can be persuaded to raise them.

"I'm pushing 77 now," said Hilbinger, a retired District of Columbia housing inspector, "but we will live to see not enough grain to feed the world. The beefalo is catching on, and I think that in less than five years you will see plenty of beefalo meat in the stores."

Massey and O'Connor are not that optimistic, largely because traditional ranchers and farmers have been slow to accept the idea of a nonconventional animal. On top of that, the breeding of pure beefalo is time-consuming; several generations are needed to work to the desired mix of three-eighths bison and five-eighths domestic bovine.

"We think there are about 50,000 beefalo out there in the United States," said O'Connor. "Our members have about 15,000 head registered; the World Beefalo Association claims 19,000 or more. The rest are there, but not registered."