Team Whitethorne LLC


Meet the women behind Whitethorne LLC, the highly successful training and sales operation out of Southern California. Led by Georgy Maskrey-Segesman, these professionals are able to make a difference through their unique skill sets that maintain Whitethorne’s high level of care, education, and performance. 

Killian McGrath

Photo © McCool Photography.

After meeting Georgy Maskrey-Segesman as a young junior rider, Killian McGrath maintained a close relationship with her. Little did she know, she would become a key member in the development and success of the organization. 

McGrath rode with Leslie Steele for 10 years, from age six to 16, where she initially met Maskrey-Segesman, who was at the time stabling one of her horses with Steele. When she made the transition to train with Karen Healy, Maskrey-Segesman coincidentally moved her horse to Healy’s at the same time as McGrath. 

“We got to know each other really well—Georgy became really good friends with my mom, and she followed my career in the equitation as a junior,” says McGrath. “When I was 19, I turned professional and she offered me a job right out of the junior ring. We basically did everything ourselves, we started just by having a couple [sale] horses at a time, and we built Whitethorne to be what it is today from that point on.”

Today, McGrath’s role involves a mix of riding, training, and managing the care and schedules of the horses, riders, and staff.

“We take anywhere from 14 to 17 horses to a show, and we have around 50 to 60 horses on our property at home. There’s a lot that goes into the 60 seconds that you see in the ring. It’s managing the horses, veterinary care, their supplements, their feed, to make sure they are all in the right program.” 

When it comes to training, riding, and teaching, McGrath puts the wellbeing of the horses first. 

“If the horses aren’t happy, you’re starting in the negatives. You have to get them sound, fit, healthy and then go from there,” she says. “For teaching, I emphasize learning the details and focusing on the basics. Without those, a lot gets lost and that’s where the issues tend to happen.”

Chelsea James

Photo © Shawn McMillen Photography.

While she may not have known it at the time, California native Chelsea James grew up not too far away from Whitethorne LLC, eventually meeting Maskrey-Segesman as a young professional. During her junior years, she rode and held a working student position at Elvenstar where she was given opportunities to develop a strong foundation to build her professional career upon. 

After aging out of her junior years, James was working in the area, and her barn had leased a couple of horses from Maskrey-Segesman and ultimately ended up moving their business to Whitethorne. 

“When I was at a point in my life where I needed some help, Georgy went above and beyond without even knowing me that well and offered to help me in any way she could,” says James. 

Photo © Sara Shier Photography.

Fast forward five years, and James went from working part-time for Whitethorne to now handling the management and operations in addition to riding, teaching, and traveling on the road. When it comes to training, she has a case-specific approach to ensure that each horse and rider is set up on the right path to reach their individual goals. 

“Some people are super goal oriented, [and] some people just want to enjoy their horses. I love helping them become the best that they can be while helping the horses be the happiest they can be. My philosophy for riding is very similar to the way I teach. I think it’s about each horse’s individual journey—listening to them and letting them tell us what they’re comfortable with.”

Ivey Burns

Photo © Laila Klinsmann Photo.

Twenty-three-year-old Ivey Burns has an all-hands-on-deck mentality when it comes to her role at Whitethorne. 

As a young rider growing up in California, Burns competed mostly on the local circuit until the end of her junior years, when she purchased a horse from Maskrey-Segesman. With that horse, Burns was able to achieve one of her goals—qualifying for and competing at the ASPCA Maclay National Championship. 

“From there, I realized that I could actually do this on a bigger level, and I started to really put more thought into if I wanted to do this as a career,” says Burns. “When I aged out, I started moving up into the bigger jumper classes, and then due to other circumstances I took some time off to really figure out what I wanted to do. I went back to school but always ended up returning to the sport.”

Burns has been a part of Whitethorne’s team since October of 2021, where she continues to learn and grow her knowledge as a professional.

“At Whitethorne, there was a need for someone to be flexible— if we need someone to go to the shows, I am able to do that, or if I need to teach or ride, I can also stay home to do that,” she says. “I am able to fill in wherever anything’s needed. I ride most of the time; when we get sales horses in, I put a lot of time into working with those horses in addition to our client and rehab horses.”

Burns enjoys working with a variety of different horses, figuring out their strengths and weaknesses, and helping them develop into the best version of themselves. As she continues forward in her professional career with Whitethorne, she hopes to expand her knowledge of and continue to hone her skills in the jumper ring. 

“Working with Georgy and the rest of the team is an amazing opportunity because Georgy never makes you feel like you can’t do it. She has so much knowledge that her instruction really makes you think of solutions you’ve never thought of,” says Burns. “I think the biggest thing that makes Georgy stand out is her dedication to bettering the sport.”

Whitethorne LLC: Rehabilitation

Photo © Bethany Unwin Photography.

In a separate venture from its training and sales endeavors, Whitethorne also offers a top-notch equine rehabilitation facility. Led by Kristi Iwamoto, the operation offers treatment not only for injured horses, but also horses who may just need a break from their everyday program. 

Iwamoto began riding at a young age, and during her junior years she held a working student position where she was able to develop strong horsemanship skills and knowledge of the animal.

With Whitethorne, she works to ensure that each horse is in the right program with the right modalities and exercise, which involves careful coordination with veterinarians. Efrain Rodriguez works alongside to take care of the horses in the rehabilitation program, utilizing his experience and knowledge as a former Olympic-level groom. 

The rehabilitation facility offers a customized aqua treadmill, a class IV cold laser, PEMF, and a cold water spa, among other treatments that expedite healing and offer preventative care. 

“A lot of the show jumping horses come in with suspensory injuries, so we often have them use the BEMER set every day, then the cold water spa to reduce inflammation, and then laser therapy,” says Iwamoto. “The cold laser is regenerative, so it increases blood flow, reduces inflammation, and has some instant pain relief.” 

For horses that may just need a bit of rest and relaxation, Whitethorne’s grass turnouts are a great option for in-between circuits or shows. The aqua treadmill allows horses to build and maintain muscle strength while having a break from a rider on their backs. 

Photo © Bethany Unwin Photography.

Regardless of the horse’s injuries or needs, Whitethorne’s rehabilitation program can customize programs to get its residents back on track to their peak condition. Combining the most innovative treatments with a high level of care, the facility is a quiet oasis, ideal for horses of all kinds. 

“With the right tools and knowledge, we can really give the horses our full attention to make sure that they have a great quality of life, either from an injury or relaxation perspective,” says Iwamoto.  “They’re more than just animals or an investment—they’re partners. We treat every horse individually, because at the end of the day, we just want to make the horses better. It’s great to be able to make a difference on some level.”

This Post Brought to You by: 

Whitethorne LLC

Whitethorne LLC always carries a number of high-quality Hunters, Jumpers and Equitation horses for sale or lease in Southern California. All of these horses are personally chosen by Georgy Maskrey-Segesman and her partner in Germany, and represent some of the best competition horses available in Europe for every level of competition in Hunters, Equitation, and Jumpers. Georgy travels to Europe several times per year and together with her partner in Germany, selects the best of the horses available in Germany and Holland and several other countries in Europe, and imports them to Whitethorne Ranch where they are available for sale or lease.

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