The Oklahoma City Zoo announced that an Asian elephant was euthanized on Tuesday due to declining health and age-related issues. >> Get the latest news stories of interest by clicking here.Zoo officials said Rex, who was about 57 years old, was undergoing care and treatment for advanced osteoarthritis and other age-related issues. Caretakers were monitoring Rex and worked closely with the Oklahoma City Zoo’s veterinary care team to develop a daily geriatric care and treatment program for Rex. Recently, the caretakers saw a decline in Rex’s physical condition, including a significant reduction in his mobility, increased stiffness and discomfort in his legs and feet, as well as difficulty moving around some of the more uneven terrain in his habitat. Zoo officials said those changes were indications of chronic pain or discomfort that were no longer able to be alleviated with medical or physical therapy. The veterinary and elephant care teams decided to humanely euthanize Rex, who died peacefully Tuesday at the Oklahoma City Zoo’s elephant barn at Sanctuary Asia. “Rex’s life and continuing legacy will not be forgotten. He was the cornerstone of the Oklahoma City Zoo’s elephant breeding program and the proud father of our three young females,” the Oklahoma City Zoo’s elephant curator Rachel Boyd said in a news release. >> Download the KOCO 5 AppRex was one of the oldest male Asian elephants in the Association of Zoos and Aquariums’ population. He first joined the Oklahoma City Zoo in 2011 from African Lion Safari in Canada and was part of a breeding recommendation. “Rex’s influence not only shaped the future of the Zoo’s herd but also our continued commitment to conservation and animal care,” Boyd said. “In North America, his enduring legacy lives on through his seven living calves and five living grand-calves, including three here at the Zoo. Rex was truly a remarkable presence, and I feel honored to have cared for him in the final years of his life.” Top Headlines Man on Oklahoma death row for killing Tecumseh police officer dies in prison Up to 4 in 10 people could develop dementia after 55. What you can do to lower your risk Pickup truck crashes into pole, leaving hundreds of Norman residents without power Oklahoma doctor gives advice on staying safe from norovirus, or ‘stomach bug’ Mustang Public Schools warns parents of cyber security incident involving software vendor