Some of the proposed sales, valued at more than $23 billion, were under review, while others were never sent to Congress. The administration is pushing them through without congressional approval.
Nearly three weeks into a war that polls show is unpopular, top Republicans have yet to call administration officials to testify about it, arguing that hearings would put divisions on display.
The walkout at the JBS plant in Greeley, Colo., comes as beef prices have soared, cattle supplies have plunged and immigration sweeps have stressed the labor supply.
People representing the three brothers have reached out to a lobbyist and an influential Jewish group that have supported clemency for others. There are no signs the White House is considering a pardon.