UPDATE 1-Ackman's Pershing Square ends 2015 with 20.5 pct drop
January 05, 2016 at 17:12 PM EST
BOSTON, Jan 5 (Reuters) - Billionaire investor William Ackman's Pershing Square Holdings hedge fund ended 2015 with a 20.5 percent loss after Valeant Pharmaceuticals, a top holding, was battered in the second half of the year.