Mary Clayton watched her daughter, Alannah, 10, stride confidently through the Barn at Spring Brook Farm and head to the pasture to walk her favorite miniature horse, Dreamer, while telling the filly about the week that had passed since her last visit.

Dreamer's half-sister, Chestnut, eyed the two pals, then walked purposefully toward Sugar, an emotionally needy miniature Sicilian donkey, which started shrieking at earsplitting volume.

Alannah kept her cool. "You're not going near that donkey," she told Chestnut, and led her away until Sugar stopped screaming. Returning to Dreamer, she explained, "They get a little jealous." And with that, Alannah and Dreamer walked on, heads together, in the afternoon sun.

Clayton said her daughter, whose autism was diagnosed when she was 3, was a quiet, withdrawn child who lacked the skills to develop friendships before she started coming to the Barn, in Pocopson Township, Chester County, five years ago.

"Her first time here, Alannah stood in the field and hugged Dreamer and said, 'Hi. I'm Alannah,' " recalled Clayton, of Glen Mills. "She smiled a big smile. She went from a flat affect to that smile on her first day."

Alannah is among 300 children with disabilities, ages 2 to 12, who enjoy animal-assisted activities at the Barn in weekly hour-long visits, supervised one-on-one by 300 volunteers in fall, spring, and summer camp sessions.

Many return year after year, living the dream of the nonprofit's founder, Mary Beth Drobish. After her husband, Bob, died in 2003, she wandered their 17-acre farm, asking herself what she'd do with the rest of her life.

She walked into a pasture and posed the question to her beloved Arabian mare, Aziza. "I love animals," Drobish told Aziza. "I love children." The black horse listened. Something happened.

"I had an epiphany!" a smiling Drobish recalled recently. "I thought, 'Oh, my gosh! Build a barn!' I couldn't find something to draw on, so I grabbed a paper towel and a pencil and began to sketch."

By 2006, the Barn was done, a big, modern building housing horses, donkeys, goats, sheep, rabbits, and a potbellied pig in ground-floor stalls that open onto a fenced pasture, and a spacious play and educational area on the second floor. Nearby, a wooden ramp leads to a handicapped-accessible tree house overlooking the farm; another ramp leads to a hayride that children in wheelchairs love.

The Barn's first visitors were from the Overbrook School for the Blind. When she saw them quickly bond with farm animals whose names are imprinted on their stalls in braille, "I knew this was going to work," she said.

"Kids don't ride horses here," Drobish said. "They feed and groom and exercise the animals." In the process, they emerge from years of solitude and insecurity to improve everything from gross motor skills to task management.

Two years ago, Pocopson Township supervisors threatened to close the Barn unless 33 alterations were made to satisfy property code requirements. The community came to the rescue, donating $100,000 and providing volunteer and low-cost help to build a second restroom, wheelchair accessible ramps and macadam paths, among other improvements.

John Milner of John Milner Architects Inc. in Chadds Ford donated his firm's services. Bob Adams, a lawyer from West Chester. provided pro bono legal help. Regester Associates in Kennett Square discounted its engineering services. Joe Schorn and the employees of Schorn Construction Co. in Downingtown donated time and materials for the tree house and ramp.

Volunteers included a crew from the First Presbyterian Church in West Chester, where Schorn and Drobish are members.

On Saturday, Drobish will celebrate the Barn's 10th birthday with a hoedown and silent auction, where supporters in jeans, boots and cowboy hats will dance to the Summit Hill Bluegrass Band and, at $100 a ticket, contribute to its privately funded $332,000 budget.

The nonprofit offers financial aid to help pay the fees. No one is turned away for inability to pay.

Hundreds of parents like Clayton are grateful the place was saved.

"When Alannah came to the Barn," Clayton said, "she would use single words to communicate what she wanted. . . . She would get frustrated and could not explain what was bothering her."

On Alannah's first day five years ago, her one-on-one volunteer, Evelyn Norton, a retired dietitian from West Chester, asked, "Do you think Dreamer wants to go for a walk? Can you help me put the harness on?"

That, Clayton said, was the beginning of a beautiful friendship, one that helped make her daughter the communicative girl she is today.

"She'd sit with the rabbits and tell them, 'I went to school today. I like music. Do you want me to sing you a song? Do you want a lullaby?' She'd sing 'Twinkle, Twinkle, Little Star.' We discovered she has perfect pitch."

Most important, she said, is that her daughter discovered confidence. "She knows she has autism," Clayton said. "Before coming here, she wanted to keep to herself. Here, you're not judged. So she lets down her guard. She's much more willing to engage and seek out friendships now. She has something to talk about with her peers at Garnet Valley Elementary School.

"She's a little miracle," Clayton said. "She has a beautiful heart, a beautiful mind, a beautiful soul."