Whenever a horse arrives at Mill Creek Farm in Florida, Peter and Mary Gregory make the aging animal a promise to last the rest of its days.

"We say you'll never be worked or ridden again," said Peter Gregory, director of the farm. "And you'll be here forever. And they are here forever because when they die here, they're buried here."

About 130 horses have this 325-acre farm in north-central Florida as their retirement home, doted on by now-elderly caretakers. Nearly all of the horses have worked for years in law enforcement, military or other service jobs; a few have been seized by police.

Now these horses graze in green pastures, under moss-draped oaks. Their tranquil existence is only broken each day by Peter, 85, and his wife Mary, 81, riding out on golf carts from their home on the property. From field to field they go, feeding the horses hay, grain and carrot treats.

"It's difficult to find any place that will take an older retired horse. We wanted Special to actually truly be retired," said Sgt. Chris Laster of the Sarasota County Sheriff's Office, who brought a 23-year-old horse to the farm for retirement in 2013. "Peter knows every horse's name there; he knows their stories."

Originally from England, the Gregorys spent years traveling the world when Peter was a hotelier. In 1984, they bought the farm about 20 miles north of Gainesville and created a nonprofit organization called the Retirement Home For Horses. It's since drawn tourists, documentary filmmakers and other visitors curious about where veteran horses go.

Some of the horses are blind. Some are ill. And all would have ended up at an out-of-country slaughterhouse had the Gregorys not taken them in. The farm doesn't accept horses from private owners. There are other horse retirement farms in the U.S. in Kentucky, Tennessee and Connecticut and there are only a few, much smaller farms for aging horses in Florida.

There's Special, a horse who worked for the Sarasota County Sheriff's Department for 17 years and whose last big event was the 2012 Republican National Convention in Tampa.

There's Possum, who came from the Army's Mounted Color Guard in Colorado, along with a certificate of achievement signed by President Barack Obama.

Christie and Butch were found abandoned and starving in Miami-Dade County.

And there's Roman, a 13-year veteran of the Orange County Sheriff's Office who helped search for little Caylee Anthony, who went missing in 2008 and later was found slain. When Roman arrived last summer, he sought out Dylan, another Orange County Sheriff's horse that had retired a few years before. The pair have stuck close to each other in one pasture ever since.

"We believe that horses shouldn't be ridden, quite honestly," said Peter Gregory. "They weren't put on earth to be ridden. Everything man does to a horse we believe is wrong. Put a bit in their mouth, put shoes on their feet, spurs and things like that."

The couple said they were inspired to start the farm by their childhood love of horses; Mary had a horse as a girl and Peter used to ride with the milkman on a horse-drawn cart in pre-war England.

Over the years, the farm has expanded in acreage and number of animals and cost.

The couple estimates they spend more than $250,000 a year to operate the farm and feed all of the horses; some of that comes from donations and another chunk from the Gregorys' retirement fund. Most of the costs are for feed in the winter but in the summer the horses graze on grass and hay.

"Right now we're buying four tons of grain a week," said Gregory. "It's a lot of money."

Veterinary care is often provided pro bono by veterinary school students.

While they do have volunteers and a part-time paid employee to help with daily chores, the Gregorys, as they also age, realize that they must form a plan for the farm's future. They do have children, but they have their own careers. A board of directors oversees the farm, but the Gregorys hope that they can find someone such as a veterinarian to deal with the day-to-day challenges.

"We have to find somebody willing to come here and manage it," said Peter Gregory.

He added a touch of dry humor: "We've been working here for 30 years and we still haven't got our first paycheck, by the way."

Gregory said that when he and his wife die, the farm will remain a nonprofit organization to help horses. The land is protected by a perpetual conservation easement that prevents the property from being developed.

It's a stunning property, with gentle hills and a small creek in the woods; the horses live in various fenced pastures while the couple's dogs roam the property during the day.

Even though the Gregorys are looking for someone to take over, they are still accepting new horses.

"Most horses, when they get old, if they do get old, then nobody wants them anymore," Gregory said.

There's a special patch of land where the horses are buried; a sign that says "Field of Dreams" stands in a clearing. A tree is planted for each horse buried in the field, marking the animals' final resting spots.