US cattle ranchers filed a lawsuit in the Lincoln District Court on Friday, alleging that the meatpacking divisions of ConAgra Foods and Cargill have been purposefully depressing the cash cattle market. If the case is accepted by the court, cattlemen who sell by taking bids from buyers on a weekly or daily basis would have to prove that the two companies use livestock contracts and ownership to depress the market, and that they have been violating the 1921 Packers and Stockyards Act by engaging in monopolistic practices.