Beef packer margins improved sharply, with estimated net losses narrowing to -$111/head from -$206/head the prior week. The recovery was driven by another firming in the boxed beef cutout, which rose to $379.00/cwt, while fed cattle prices softened modestly on the week. Even with the improvement, packer profitability remains negative and continues to reflect tight cattle supplies and elevated procurement costs. Packers should see weaker fed cattle prices again this week amid the impacts from the 7-day labor strike at the Greeley, Colorado JBS plan, which is pushing some 29,000 head to other slaughter plants.  Southern Plains feedlot placement margins remained ...