William Thomas Riddle, DVM, a co-founder of Rood & Riddle Equine Hospital in Lexington, Ky., passed away Sept. 20, 2026. He was 74.

Riddle was a self-proclaimed “horse nut.” He was a world-renowned authority on equine reproductive medicine. In 1982, he and Dr. William Rood partnered to establish Rood & Riddle Equine Hospital.

“I was saddened to learn of Dr. Riddle’s passing,” Rood says in a statement released by the hospital. “I will miss Tom’s wise counsel, his entrepreneurial spirit and his gentle ways. He was the best partner, and together we accomplished more than we dreamed. Tom will be missed.”

Riddle served as president of the Kentucky Association of Equine Practitioners, the Society of Theriogenology and the Theriogenology Foundation. He earned numerous honors throughout his career, including Steiner Award for Excellence in the Practice of Theriogenology, the Friend of University of Kentucky Ag Equine Programs, UGA College of Veterinary Medicine Dean’s Distinguished Service Award, and the Distinguished Educator – Mentor Award from the American Association of Equine Practitioners (AAEP).

“Dr. Riddle’s immense contributions to the field were matched only by his unwavering integrity, humility, and passion for inspiring the next generation of equine veterinarians,” according to a statement by the AAEP. “His legacy endures through the many theriogenology interns he mentored who not only went on to achieve board certification but become influential mentors in their own right — a lifetime of transformative impact commemorated in 2024 when AAEP deservingly bestowed its Distinguished Educator – Mentor Award upon Dr. Riddle.”

Riddle founded Hats Off to Kentucky’s Horse Industry Day, which celebrates the horse and its profound effect on the state of Kentucky. In 2023, he was appointed to the Kentucky Horse Racing Commission by Gov. Andy Beshear.

Visitation will be from 4-7 p.m. Sept. 28 at Clark Funeral Home, Rose Hill, in Versailles, Ky. A memorial service will be at 11 a.m. Tuesday, Sept. 29, 2026, at the Church of the Ascension in Frankfort, Ky.

In lieu of flowers, memorial contributions may be made to the Bluegrass Farms Charities, P.O. Box 12252, Lexington, KY 40582, or donate to www.bgfcky.org.