Senate Judiciary chairman Charles Grassley asked the Justice Department for an antitrust review of an agreement for JBS, the giant Brazilian meatpacker, to buy the pork operations of agribusiness rival Cargill for $1.45 billion. When the deal was announced on July 1, the companies said it was subject to antitrust review. JBS is the second-largest meat processor in the United States and Cargill is No. 3. If the sale is approved, Grassley told reporters, the four largest pork processors would own 71 percent of slaughter capacity. “You have the possibility of reducing competition” at the expense of hog producers, he said.