Tina Nunn was taking beginning riding lessons back in 2004 when she bought Rose, a retired thoroughbred with an uncertain future.

A former turf racer, Rose was for sale, but she didn’t fit a niche in the horse market, said Nunn.

She couldn’t be a hunter-jumper because of damage to her legs from racing; she was too high-strung to be a lesson horse and was too big for most prospective owners.

“A horse needs to have a purpose,” said Nunn. “She didn’t have a niche, other than to be loved by me.”

“She and I just clicked,” said Nunn last week on a visit to Rockville Equestrian Center, where she now boards her 10-year-old “pleasure horse,” as she calls her.

Now it turns out that the unwanted horse that Nunn took in has a distinctive pedigree, with one of the most famous racehorses of all time in her lineage.

At the suggestion of Jennifer Wright of Three Oaks Equine, Nunn started researching Rose’s lineage online.

“It’s like researching the genealogy of the family,” she said.

Using the tattoo number (C11997) on Rose’s lip, it didn’t take long for Nunn to find out that 1973 Triple Crown winner Secretariat was her ancestor.

“I always knew she was special. Now it’s a fact,” said Nunn.

For Nunn the discovery was an exciting surprise, but coming five years after she bought Rose, the information played no part in her decision to buy the horse.

“I knew she was a race horse but I didn’t care,” said Nunn of her decision to buy Rose. “It just goes to show you can be unwanted one day and racing royalty the next.”

Nunn, 44, said her two daughter also love to ride, and both take lessons at Rockville Equestrian.

Nunn said Rose’s story points out some of the less glamorous aspects of thoroughbred horse racing that the public rarely sees.

“I’m not a big fan of the thoroughbred racing industry,” she said. Nunn says the horses are exploited for profit and then many are cast aside, some being sent to Mexico for slaughter.

But that’s not in the cards for Rose, thanks to Nunn. Now all Rose has to look forward to is a graceful retirement.

“I may be foolish,” said Nunn, who noted that keeping a horse is a big expense, “but she’ll be safe and loved and cared for the rest of her life.”