FOR a mere $5.95, a lover of horses can spend an entire day in heaven. That's the price of the admission to the Kentucky Horse Park, in the countryside outside Lexington, where one can rub noses with many of the aristocrats of the horse kingdom. Of course, it's a joy just driving the back roads in this lush green land where undulating white or black plank fences outline the pastures and surround the hilltop buildings of Kentucky's bluegrass horse domains. Here, too, mares and their foals crop and romp in their own paddocks, and the stallions reign, each in his own. Double fences put eight feet of space between the stallions' paddocks to keep the high-strung creatures apart.
And at intervals there are the long, tree-lined drives leading to the old Kentucky homes of farm owners.
But we are not invited in. Until a few years ago, even at farms where stallions worth millions of dollars were stabled, visitors were welcome. Sadly, so many guests abused the privileges - leaving gates open, feeding the animals, scattering trash - that the inner workings of these private estates are no longer on view.
``And that,'' says Mimi Lewis, Kentucky's commissioner of tourism, ``is the reason for the Horse Park. Here there is all you could see at the horse farms, everything you ever wanted to know about horses, rolled into one complex of stables and paddocks and tracks.''
Not to mention exhibit halls where, at the start of this total horse-embracing day, you can watch the lovely wide-screen film ``Thou Shalt Fly Without Wings'' and be carried away into every corner of the world where horses work and play. The film covers everything from the galloping of wild mustangs on the prairie to the bruising melee of the polo field, to the ballet of the Lipizzans, to the plowing of a New Hampshire field.
After which, put it all in perspective with a walk on a spiraling ramp past murals depicting the history of the horse, going back to prehistoric times. Or, just around the corner, burst dramatically into the golden age of the horse where, against a black background, spotlights play on such picturesque vehicles as a stagecoach pulled by two sturdy teams or a wicker pony cart, and on the victorias and broughams and basket phaetons that carried the gentry of the 19th century to tea parties and balls.
Although 32 breeds of horses are stabled at the Horse Park and can be seen on parade or in their stalls, a serious student of this noble animal should be sure to look up the lighted portraits of 63 breeds, also in the Museum of the Horse Exhibit Hall. While there, if you want to know the facts about a particular breed, you need only press a button and it all comes up on a computer screen.
After viewing the dazzling array of silver and gold trophies - bowls, statuettes, platters, and cups - won by the eight Kentucky Derby winners and the 100 or more Stakes winners raised at Calumet Farm, it's time to leave this indoor, Epcot-like center of horsedom and get out into the living, horseflesh world of stables and fields.
Twenty-eight miles of white board fences divide the farm's prime bluegrass into the exercise paddocks and grazing fields. At any given time one can see gatherings of the park's 200 horses.
Polo fields, where matches are held every Sunday afternoon; steeplechase tracks; and ``eventing'' fields, scene of an international three-day event attracting top riders to Kentucky every spring - all these are framed in that classic white. The fences even surround the 14 farm buildings of what was the Walnut Hall Stud Farm, which now, as the core of the Horse Park, belongs to the state.
The park is a working farm. You can stop by the blacksmith shop and watch the farrier, backed up against the shoulders of a Belgian draft horse, pounding nails into the huge shoe into the hoof he holds so tightly between his knees. This he does every six weeks to each horse on the farm.
In the old-time harness shop next door, the harnessmaker, as the visitor looks on, works the leather for a bridle that will adorn a white Arabian, or perhaps a Morgan, in one of the daily parade of breeds put on for the curious public.
But better than the parades, or the shops - better even than the view from a five-passenger surrey, of the labyrinth of fences and the gorgeous creatures contained therein - is the Hall of Champions. This is the barn in which Kentucky's bluest bluebloods are so munificently lodged, befitting their elevated status. Here, in the paneled and spacious box stalls where the proud stallions of the Walnut Hall Stud Farm were once housed, A Letter to Harry, John Henry, Forego, Rambling Willie, and other equine greats that are no longer productive loll knee-deep in mint-condition straw.
And in the paneled ``lobby'' of this equine hostelry, visitors can stand in the open Dutch doorways leading to the stalls and have a good old heart-to-heart with Forego, for instance, about his sensational finish in the Marlboro Cup race of '76, and with Rambling Willie, once king of the standard-bred pacers. That's about as close as you can get to royalty.
Write to Kentucky Horse Park, 4089 Iron Works Rd., Lexington, KY 40511. Tel. (606) 233-4303. The park is just off Interstate 75 at Exit 120. The park is open all year except for major holidays. Hours are 9 a.m.-7 p.m. Memorial Day through Labor Day; 9 a.m.-5 p.m. otherwise.
Trail rides are available down scenic paths around the back portion of the park. Pony rides are available for children. Adjacent to the park is a luxurious resort campground, with a swimming pool, tennis and basketball courts, even miniature golf. And for campers, remote sites can be had. The cost is $10 a night in the prime summer season.
Incidentally, ``bluegrass'' is blue only in late May or early June when it's in blossom. The rest of the year the grass is a deep green, made special by the geometric overlay of the fences.