The legal arm of the United Stockgrowers of America has filed suit to block the proposed merger of Greeley-based meatpacker JBS Swift and National Beef Packing Co.

The suit, filed in U.S. District Court in Illinois by the Ranchers-Cattleman Action Legal Fund and the Organization for Competitive Markets, follows separate legal actions by the U.S. Justice Department and 17 state attorneys general.

"We believe our involvement will assist the government's case because we can fully represent the views and competitive concerns of farmers, ranchers and feeders who are most affected by this merger," Bill Bullard, CEO of the Ranchers-Cattlemen Action Legal Fund, said in a statement.

Bullard said his group and the Organization for Competitive Markets have collaborated since March to seek legal action from the Justice Department and numerous state attorneys general, not only against the National Beef acquisition but also JBS' recently approved purchases of Smithfield Beef Group and Loveland-based Five Rivers Ranch Cattle Feeding.

"Because of the profound impacts this proposed merger would have on U.S. cattle producers, the thousands of domestic cattle farmers and ranchers cannot be sideline observers in this historic lawsuit," Bullard said. "Even without the Smithfield and Five Rivers components, this is the largest and most compelling merger ever contemplated in the U.S. cattle industry and it would radically restructure the U.S. cattle markets."

Fred Stokes, executive director of the Organization for Competitive Markets, said the suit takes the anti-trust action by the Justice Department to a new level. "While we share an interest in defending our U.S. antitrust laws, we also have a unique perspective regarding the adverse effect this merger would have not just on competition as a whole, but on individual cattle producers as well," Stokes said. "We are proud to join this fight to preserve our cattle markets for independent cattle producers."