Tyson Foods, the largest U.S. meat company, is close to acquire Keystone Foods, which supplies chicken nuggets to McDonald's, from Brazil's Marfrig Global Foods for as much as $3B, Bloomberg reports.Marfrig said in May that it selected five bidders for the final phase of the sale process, and Tyson  now is said to be in exclusive talks about a potential deal.Keystone's 2017 revenues totaled $2.8B,...