WHEAT MIDDLINGS IN HIGH-CONCENTRATE DIETS - FEEDLOT PERFORMANCE, CARCASS CHARACTERISTICS, NUTRIENT DIGESTIBILITIES, PASSAGE RATES, AND RUMINAL METABOLISM IN FINISHING STEERS

We conducted two experiments to determine the feeding value and effect s on diet digestibilities, passage rates, and ruminal metabolism of wh eat middlings (WM) fed as a replacement for either the concentrate or roughage components of finishing diets of steers. In Exp. 1, 120 mediu m-framed steers were blocked by weight and randomly allocated to one o f six treatments of high-concentrate diets: control (0%); 5, 10, or 15 % pelleted WM replacing dry-rolled corn (DRC); and 5 or 10% pelleted W M replacing chopped alfalfa hay (ALF) components of the diet. Increasi ng WM replacement of DRC increased DMI(P < .01) and feed:gain ratio (F G; P < .05) linearly. A 9.2% increase in daily DMI and 10.1% increase in FG were observed at 15% of WM. Daily gain and final weight of the s teers were not influenced by WM replacement of DRC. The WM replacement of ALF decreased (P < .01) daily DMI linearly, but it had no effect o n ADG, final weight, or FG. In Exp. 2, six medium-framed steers, fitte d with ruminal cannulas, were used in a 6 x 6 Latin square design with the same treatments as described in Exp. 1. Dry matter, OM, and starc h digestibilities decreased (P < .01) by increasing replacement of DRC with WM, and replacing ALF increased DM and OM digestibilities linear ly (P < .01). Wheat middlings could replace only up to 5% of DRC witho ut reducing feed conversion efficiency and diet digestibilities, but c omplete (100%) or partial (50%) replacement of ALF increased digestibi lities of DRC finishing diets.