SEATTLE -- Loaded in climate-controlled crates aboard a flatbed truck and accompanied by an entourage and special snacks, two aging female elephants have left a Seattle zoo on a 3,200-kilometre trip to their new home in Oklahoma City.

The Wednesday evening departure was emotional for both Woodland Park Zoo workers and for elephant activists after a federal appeals court declined to block the transfer.

"It was a difficult day for staff and volunteers, especially for those of us who have cared for these elephants for years," Seattle zoo spokeswoman Gigi Allianic said in an email. "We care for them deeply and love them. Yes, we're sad to see them go -- like sending your kids off to college and saying goodbye -- but we're doing the right thing for Bamboo and Chai. We are excited for them."

A panel of the 9th U.S. Circuit Court of Appeals denied a motion by activists to stop the move to the Oklahoma City Zoo.

Woodland Park Zoo President Deborah Jensen said in a statement that officials were grateful for the court's decision and were focused on the elephants' welfare. Zoo officials have said the elephants will be able to join a larger, multigenerational herd in Oklahoma City.

Activists have said the long trip could endanger the elephants' health and that their quality of life in Oklahoma would be worse than in Seattle. The trip was expected to take about 40 hours.

The legal action was part of the broader debate about whether housing elephants in zoos is humane, with critics arguing the large animals need more space than zoos can provide. Activists wanted them sent to a sanctuary.

Bamboo is 48; Chai is 36.

Alyne Fortgang, a co-founder of the Elephant Justice Project, joined other activists at the zoo when it was clear the move was imminent. Some of them wept.

"This is not about us being heartbroken," she said. "This is about the elephants -- our humanity and how we treat these other beings."

She called it "a sad day for the citizens of Seattle."

The Seattle zoo said three elephant experts, two veterinarians and the transport consultant staff will accompany the truck.

"The trip will be straight through except to stop every few hours to check on the animals' well-being and to provide food and change water," Allianic said.

Two months of crate training for the elephants helped the loading go smoothly, she said.

The zoo "'packed a trunk' for our elephants," said mammal curator Martin Ramirez. The "road trip" food included 660 pounds of hay, as well as supplies of watermelon, cantaloupe and honeydew melon.

The Woodland Park Zoo estimates it will cost $111,000 to ship the elephants. They will be on a long-term loan.

The zoo has said the transfer will also give the pair more space. The zoo considered a number of U.S. zoos with Asian elephants before deciding the Oklahoma City Zoo was the best choice.

The Elephant Justice Project had asked the city of Seattle to block the move.

The Seattle City Council passed an ordinance in 2001 transferring the management and ownership of the zoo to the non-profit Woodland Park Zoological Society. But Mayor Ed Murray asked that the zoo consider sending the elephants to a sanctuary or a home where they would have more space and live in a warmer climate.