Complex sentence: He began treatment while continuing to rest at Winstar, and after gaining back 110 pounds in two months, was returned at last to Pletcher's barn at Saratoga on July 11,2011.
Split into simpler sentences: He began treatment while continuing to rest at Winstar. After gaining back 110 pounds in two months, he returned to Pletcher's barn at Saratoga on July 11,2011.