Thanks in advance!

What kind of racing? Saddle racing or harness racing? Paced or at the gallop?

Each type of official race is limited to particular breeds. For example, thoroughbred races can only be entered by thoruoghbreds who have the correct paperwork and are DNA identified. Harness racing is for standardbreds. Quarter horses and other breeds (particularly paints and arabians) may have their own racing organisations. This limits you to which breeds you can enter.