The meat processor said nine of its more than 100 plants would suspend operations for the day because of an expected lack of workers.

A nationwide series of boycotts and marches are planned for May 1 by pro-immigrant activists as part of an effort to urge Congress to grant amnesty to the estimated 11.5 to 12 million unauthorized immigrants living in the United States.

"We understand the sentiment behind the May 1st events, but we are not encouraging workers to participate in the rally," Tyson spokesman Gary Mickelson told CNN.

Mickelson said the nine Tyson (down $0.07 to $14.48, Research) facilities that will be closed are red meat plants, but he would not reveal which specific plants would be closed.