Wheat Middlings as a Source of Energy, Amino Acids, Phosphorus and Pellet Binding Quality for Swine Diets

Two performance trials and a N-energy balance trial were conducted to evaluate wheat middlings (midds), processed from Michigan soft white winter wheat, in pelleted swine diets. In Exp. 1, midds replaced corn on an equal-weight basis at 0, 10, 20 and 30% of the diet. Diets were calculated to be nutritionally adequate during the starter, grower and finisher phases. Increasing the level of midds in starter diets increased (P<.01) the feed required per unit of gain (F/G). Feed consumption increased with increasing levels of midds during the finisher phase, with no appreciable increase in average daily gain (ADG). Overall (16 wk), there were linear increases (P<.01) of feed intake and F/G with additions of midds. There was a linear depression (P<.01) of loin color, firmness and marbling scores as percentage of midds in the diet increased. Swine grower and finisher diets in Exp. 2 were formulated to take advantage of the lysine (.69%) and P (.90%) values of midds and the pellet-binding qualities of midds. Midds were incorporated into diets at 0, 20, 40 and 60%. Overall, ADG was linearly depressed (P<.01) with increasing levels of midds. Feed/gain linearly increased (P<.01) with increasing levels of midds in finisher diets. Yield and metatarsal ash decreased (P<.01) linearly with increasing levels of midds. Diets containing midds required more (P<.01) force to crush pellets than diets containing a pellet binder. The addition of midds did not reduce apparent protein digestibility (APD), whereas the 20% midds diet maximized apparent biological value (ABV) and net protein value (NPV). Diets containing 40 and 60% midds depressed (P<.01) ABV and NPV. By extrapolation of efficiency of gain data from the finishing phase of Exp. 2, the metabolizable energy of midds was estimated to be 2.99 kcal/g.