July 9, 2025 
Earlier this week, American rider Bliss Heers’s top horse and partner of seven years, the 15-year-old stallion Antidote de Mars, passed away unexpectedly from a stroke.
“I’m so grateful for every moment that we had together and for everything that you did for me,” Heers wrote on Instagram on Wednesday. “I love you and thank God for you everyday.”
His name was Antidote de Mars, and it suited him well.
Heers first met the stallion back in 2018, at a time when she needed a bit of a remedy herself. That spring, Heers was riding a fresh, 5-year-old stallion before a horse show when he unexpectedly reared and flipped over on her.
She broke the wings on her L1-L5 vertebrae, her pelvis, and dislocated a hip. But Heers miraculously escaped without internal damage, and within a few short months, she was at the barn again—then back competing internationally. But other aspects took longer to heal.
Before her injury, Heers had been living in Europe for six years, first training under Otto Becker in Germany, and then eventually striking out on her own in the Netherlands. By 2018, she was starting to feel frustrated, still struggling to gain a foothold in the industry.
“I wasn’t close to a five-star or even a two-star Grand Prix,” Heers told Sidelines years later. “I was beginning to feel lost and like I may never really make it as a top rider.”
In cases like these, the ‘antidote’ for becoming a top rider is, of course, a top horse. And Heers found that in both name and talent in the then-6-year-old, Selle Français stallion by Diamant de Semilly.
“My parents were looking to support me with a nice young horse that potentially had a big future ahead to kind of get me back into the sport,” Heers explained in a video for Genesis Horse Breeding, which listed Antidote’s sister for sale.
“His heart is his best quality. He’s very careful, he’s very scopey, but it doesn’t matter what you do, he will go through fire for you. He has all the qualities, but for me, the heart and the brain are most important.”
Together, Heers and Antidote jumped clear for the winning U.S. Team in their first CSIO4* Nations Cup appearance in Wellington in 2021, a performance that helped to both put them on the map and the short-list for the Tokyo Olympic Games.
That August, they won both the Welcome and the CSI3* 1.60m Grand Prix in Traverse City, going on to jump 0/1 for the USA in the CSIO5* Nations Cup at Spruce Meadows in September, an appearance that Heers has referred to as “her best memory.”
Their reign continued throughout the fall, with consistent, top-10 placings at Spruce Meadows and in Major League Show Jumping (MLSJ) competition at events including San Miguel de Allende and Monterrey (La Silla) in Mexico, and Thermal, California.
In 2022, the pair earned a career-first, CSI5* Grand Prix win in Team Competition at MLSJ San Miguel de Allende, a feat they repeated in Team Competition at MLSJ Thermal two months later.
“I can always count on Antidote,” Heers said after that first victory. “He’s a gift from God. He’s a unicorn. There are no words to describe him.”
That same year, Heers and Antidote finished third on the podium in both the 1.60m ‘Saturday Night Lights’ CSI5* Grand Prix in Wellington and in the LGCT Grand Prix of Valkenswaard in August. In the summer of 2023, they made their debut together in the 1.60m Turkish Airlines-Prize of Europe and the RWE Prize of North Rhine-Westphalia at CHIO Aachen.
This Friday, July 4, Antidote de Mars was taken to the vet clinic after he began acting strangely. On Saturday morning, July 5, he passed away from a stroke.
“You’ve been my best friend since we’ve met,” Heers wrote to Antidote in her Instagram tribute. “You made me believe that we could, because you could.”
