Tyson Foods Inc., the world's largest poultry producer, called off a $3.2-billion purchase of IBP Inc. that would have made it the nation's top beef and pork producer. The decision was announced nine days after IBP said an investigation into its appetizer unit, DFG Foods, uncovered potential manipulation of financial records, product theft and mismanagement by former unit managers. IBP said it was shocked by Tyson's announcement. Shares of Tyson shot up $3.15 to $14.65 in after-hours trading after closing unchanged at $11.50 on the New York Stock Exchange. IBP closed off 16 cents at $22.79 on the Big Board, then plunged to $15 in after-hours trading.