Beef packer margins were positive for the second straight week with holiday grilling demand supporting the beef market and packer profits. Packers have done an incredible job managing margins this summer and in just  three weeks swung from the deepest losses on record to well above breakeven levels. Gains across the beef complex were key in creating this improved profitability while last week’s steady/lower trade in fed cattle also helped.  The mixed trend in feedlot profits continued ...