Osage Animal Hospital

1500 West Osage
Duncan, OK 73533



Tristan J. Graf, DVM

Dr. Tristan grew up in Marlow, Oklahoma, and was destined to be a veterinarian. He followed in the footsteps of his father, Dr. Lyndon Graf, who started Marlow Veterinary Clinic. He attended Tabor College for the first two years of his undergraduate education, then transferred to Oklahoma State University for the remainder of his undergraduate training. Dr. Tristan was accepted into the Oklahoma State University College of Veterinary Medicine after only three years of undergraduate work, and received his Doctor of Veterinary Medicine Degree in spring of 2004.

While at OSU, Tristan met his wife, Dr. Kathy Graf, who is also a veterinarian. They both worked at small animal hospitals in Idaho and then Iowa, before returning to Oklahoma in 2011. Dr. Tristan's special interests in veterinary medicine include small animal dentistry and surgery.

Dr. Tristan has many hobbies, including hunting, golf, fishing, camping, and woodworking. He enjoys spending time with his wife and their cats, Grizwald and Jax. In the fall and winter months he can typically be found in a tree stand when he is not busy working at the clinic. 

Kathy Graf, DVM, DACVIM

Dr. Kathy grew up on a small farm in Kelley, Iowa. She knew she wanted to be a veterinarian at an early age and attended Iowa State University to achieve that goal. She was accepted into the Iowa State University College of Veterinary Medicine after three years of undergraduate training and received her Doctor of Veterinary Medicine Degree in the spring of 2000. Following graduation, she pursued further training by completing a small animal internship at Alameda East Veterinary Hospital in Denver, Colorado. She was then accepted into the small animal internal medicine residency program at Oklahoma State University. During her time at OSU she became Board-Certified in Internal Medicine and also met her husband, Dr. Tristan.

Dr. Kathy worked in Emergency and Specialty Veterinary Hospitals in Idaho and Iowa before moving to Marlow. Her areas of interest at work include ultrasonography, endocrine diseases (such as diabetes and thyroid conditions), chemotherapy and treating chronic gastrointestinal disorders.

When she is not working, Dr. Kathy enjoys running/exercising, gardening, reading and hiking.

Will Bernhardt, DVM

Dr. Will is originally from Marlow, Oklahoma. Dr. Will developed his interest in large animal medicine while growing upon his family's ranch, where they run a large commercial Angus cow/calf operation. He attended Oklahoma State University, where he earned a B.S. degree in Animal Science in 2011.  Following graduation, he was accepted into the OSU College of Veterinary Medicine. He received his DVM degree from OSU in 2015.  

Dr. Will is a busy veterinarian!  He performs surgeries for the Stephens County Humane Society, works at several different sale barns for both cattle and horses, and is now working with us part-time.  His areas of interest for small animals include orthopedic surgery, anesthesia and pain management, and radiograph (x-ray) interpretation. When he is not working, he enjoys duck hunting, reading books and cheering on the Green Bay Packers!