UPPER MARLBORO, Md., April 14, 2013—Leighton Farm begins a clinic series focused on the retraining of thoroughbred horses today. The clinics run through August 24 and all proceeds will benefit Thoroughbred Placement Resources, a non-profit organization which focuses on the retraining and placement of thoroughbred horses.   The clinics are designed to demonstrate the versatility and trainability of thoroughbred horses, as well as educating owners and addressing the specific needs of the horses