Boxed beef continued its strong August run on Tuesday, with Choice up $2.96 to $407.20/cwt and Select up $2.62 to $379.76/cwt, widening the spread slightly to $27.44. This marks 11 gains in the last 13 sessions, with Choice up a total of $45.88 so far this month, the highest August rally in history.   Primal values were mixed, but the Rib ($611.97) and Round ($358.70) both set new highs for the year, while the Loin pushed to $505.68 and the Brisket gained to $347.55. Loads totaled 103.