Belinda Hargreaves, a 37-year-old doctoral student, looked at several animal and poultry sciences programs before settling on Virginia Tech's Middleburg outpost two years ago.

Besides the scholarship she was offered, there were some intangibles that brought her to the site on Sullivans Mill Road. On top of the professional facilities and fine instruction, she said, there was the neighborhood--with the fox hunts, steeplechases and horse shows that attracted her to her field of study in the first place.

"Why, it's perfect," she said recently, standing in a field being nuzzled by some mares and their foals that are university property.

"I really like it out here," said Carey Williams, 23, a master's candidate from Wisconsin who has been garrisoned at the farm since June. "I grew up in a small town, and I like getting away from all the traffic and all the bustle."

It has been 50 years since philanthropist Paul Mellon, who died Feb. 1, donated the 419-acre farm to Virginia Tech, and on Friday all manner of dignitaries were on hand to celebrate the occasion. Although it is marking its golden anniversary, the Middleburg Agricultural and Research Extension (MARE) Center has been conducting equine research only for the last 10 years.

Before that, the graduate students and their professors--all of whom live at the site--studied the diets of other grazing animals raised for food and other commodities, looking for ways to improve the quality of their meat, hides and hair. Alvin Harmon, 64, who has been at the farm for 40 years and is its general manager, witnessed the switch-overs.

"They changed for the market," he said in an interview early this summer. "First they went for cows, then sheep, now horses."

The latest change came after Mellon made a $2 million gift for that purpose in 1986. It was not universally approved, since there continue to be animal scientists who dismiss equine studies, said Janice Holland, 30, a research associate at the farm who received her doctoral degree there.

"They say that because it is a companion animal, it doesn't qualify as livestock," she said.

Of course, the half-dozen researchers at the facility, where there are usually about 100 horses, don't agree with that assessment and point to the hundreds of millions of dollars spent annually on the industry. In Fauquier County alone, horse sales in 1997 were more than $8.6 million, according to the most recent agricultural census report by the U.S. Department of Agriculture. In Loudoun, the 1997 sales figure was $6.5 million.

The research at the facility is conducted through professors in Blacksburg, where Virginia Tech is based, and overseen by Holland and Wendell Cooper, the farm's superintendent. "But everybody knows what everyone is doing," Holland said. "You have to."

Holland said the slow pace of the farm and the close quarters of the research are a departure from the typical routines of college life. But that can be a good thing, she said.

The research focuses on horses' diets and how they affect every aspect of equine life, from early development to old age. Its object is to improve their health, stamina, fleetness and agility and to breed horses with better conformation. It is an area that the researchers say has been neglected, just as human diet was neglected as a serious area of study for a long time. "But it really is one of the most important things," Hargreaves said.

Before beginning her studies at Virginia Tech, she trained jumpers in New Jersey, having come from her native England during her early twenties. "It was really crazy, if you think about it. We were feeding them anything. . . . We were feeding the old horses the same as we were feeding the young."

She said "horse people" could be hard to reach on the point of diet, "because, really, they're kind of known for doing their own thing."

The horses are grouped into various pastures, with mares and their foals in one, yearlings in another, two stallions in another. The researchers, along with the farm hands, are out every day feeding them and closely observing their appearance and behavior.

At least once a month, the horses involved in ongoing research are brought into a barn near the low-slung research building; blood is drawn and other tests, such as X-rays and ultrasounds, are performed. It is from these data that the test diet being developed can be assessed.

When they're not in the pasture, the researchers work in a laboratory building and spend much of their time requesting research literature to be mailed, faxed and e-mailed from the Virginia Tech library. Spring, the breeding and foaling season, is one of the busiest times at the center.

Fall is busy, too, but for other reasons: That's when all the yearlings are auctioned off in an annual event that draws ever larger crowds. Oct. 10 will mark the eighth year of the auction, which raises an average of $70,000 from the sale of about 20 horses for the facility's upkeep, Holland said.

Cooper said commercial sellers of horse feed are beginning to incorporate some of the findings of the MARE Center into their products: "It's coming right now; they're in the process," Cooper said.

Among the findings are that a higher-fat, higher-fiber diet leads to healthier and more robust animals. Other studies deal with calcium and phosphorus levels and the amount of protein needed for optimal development of foals and yearlings.

Holland said the natural setting of the farm gives the research there more credibility.

"This is ideal," Holland said, standing in the middle of a field, surrounded by yearlings. "This is how horses are kept, in pasture."

CAPTION: Janice Holland, a research associate at the Middleburg Agricultural and Research Extension Center, nuzzles up to one of the center's horses.

CAPTION: Holland, left, and students Belinda Hargreaves and Carey Williams walk in from farm's pastures.