WEST PALM BEACH, Fla. – Florida's top veterinarian on Tuesday blamed the deaths of 21 elite polo horses on an overdose of a common mineral that helps muscles recover from fatigue. Florida's state veterinarian, Dr. Thomas J. Holt, said toxicology tests on the dead horses showed significantly increased selenium levels. The horses from the Venezuelan-owned Lechuza Caracas team began collapsing April 19 as they were unloaded from trailers at the International Polo Club Palm Beach in Wellington before a championship match. Some died at the scene, others hours later...