Beef packer margins deteriorated further last week, extending their move into negative territory after early December’s strong profits. Margins fell another $65/head to –$140 as fed cattle prices held firm while the Choice cutout slipped nearly $2/cwt. The tightening spread reflects seasonal softness in boxed beef demand colliding with resilient cattle prices. With beef demand expected to fade further into early January, packer margins remain vulnerable unless cattle prices soften materially. The Cattle on Feed report’s implications of a record number of long-fed cattle should help pressure near-term cattle prices and aid packer margins.  Feedlot placement margins worsened last week and fell ...