Some of the world’s most prominent hedge fund managers suffered losses last month as the U.S. stock market’s rally stalled, but most are still boasting gains for the quarter. William Ackman’s $20 billion Pershing Square Capital Management, which ranked among last year’s best performers with a 40 percent gain, dipped 3.1 percent in March as shares in Herbalife Ltd, a stock he bet would fall, climbed anew. For the year, however, the fund has gained 3.5 percent, an investor said on Thursday.