The 15-year-old from Bavaria, whose parents are part-time farmers, has trained her cow Luna to show jump just like a horse.
Luna, spurred on by treats such as carrots and lumps of sugar, can now jump over one metre-tall obstacles.
It all started when Regina's parents knocked back her pleas for a horse. Regina, from the town of Laufen near the Austrian border, was a keen horse rider from the age of seven but her mother and father thought she was still too small for her own horse.
But Regina refused to take the refusal lying down. “Since we had a barn full of cows, I thought I'd just try it,” she recalled.
Her first choice, a calf named Lilly, was stubborn and wouldn't co-operate with the then nine-year-old Regina. But when calf Luna was born, a wonderful girl-cow friendship was born with her.
“She wasn't shy, in fact she came straight to me,” Regina said. “At the start, I'd walk with her for hours and at some point I realised you can ride a cow like a horse.”
For tips, Regina consulted a Swiss cow school run by Anne Wiltafsky, a philosopher. Regina's friends thought the idea of riding a cow was hilarious. But soon they were asking if they could ride Luna as well.
“But only my best friends are allowed to do that,” Regina said. “Now, Luna pretty much belongs to me. She is the only one on the pasture in summer and also has her own place in the stalls.”
As a result, Luna has two feet each in the world of cows and the world of horses. The other cows in the stalls don't like Luna. And Luna herself seems to prefer the company of horses.
“Luna keeps running after the horses and trying to have contact with them but the horses aren't interested,” Mayer said.
After a while, riding alone got boring, so Regina decided to try jumping.
“I had to trick Luna and lure her with carrots and sugar. Now she is jumping a metre.”
But the cow can only make about eight jumps in one ride. “Then Luna is tired and wants to ride back to the safety of the stall,” Mayer explained.
Mayer is aware of only one other girl – in East Frisia – who has a similar hobby. “But she only rides. She doesn't jump like I do with Luna,” she said.
Veterinarians have no objection to Regina's conversion of a cow to a horse, Regina's father said. After all, horses weren't originally in the habit of show jumping.
Regina hasn't given up on her dream of having a real horse.
“Even though I'll always keep Luna and ride on her, I'm still hoping for a real horse,” Mayer said.