Effects of Ruminally Degradable Nitrogen in Diets Containing Wet Distiller?s Grains with Solubles and Steam-flaked Corn on Feedlot Cattle Performance and Carcass Characteristics

Wet distiller?s grains with solubles are the most common feedstuff generated by the ethanol industry, and this feedstuff has been utilized by the feedlot industry. Exploration of the effect of dietary distiller?s inclusion on the form and quantity of protein or nitrogen (N) has received little attention. Assessment of degradable N needs in diets containing wet distiller?s grains with solubles (WDGS) is needed to aid the cattle feeding industry in managing feed costs and potential environmental issues. In Exp. 1, 525 yearling steers (initial weight = 373 ?13 kg) received treatments in a 2 ? 3 1 factorial. Factors included corn WDGS (15 or 30 percent of DM) and non-protein N (NPN; 0, 1.5, or 3.0 percent of DM) from urea. The control diet without corn WDGS contained 3.0 percent NPN (1.06 percent urea) and cottonseed meal. Overall gain efficiency among steers fed 15 percent corn WDGS was greatest for 1.5 percent NPN and least for 0 percent NPN (P = 0.07, quadratic), whereas gain efficiency decreased linearly (P < 0.09) as NPN increased in the 30 percent WDGS. Dressing percent was greater (P < 0.01) for the control diet than for 15 percent or 30 percent WDGS. In Exp. 2, 296 steer calves (initial BW = 344 ? 12 kg) were adapted to a common finishing diet, blocked by BW, and assigned to treatments. Experimental diets included a control diet without WDGS (contained 3 percent NPN from urea, and cottonseed meal) and 15 percent WDGS with either 1.50, 2.25, or 3.00 percent NPN (0.52, 0.78, and 1.04 percent urea, respectively, on a DM basis). Overall gain efficiency on either a live or adjusted basis was not different among treatments (P > 0.15). Dietary NPN concentration did not influence growth performance (P > 0.21). Results suggest that optimum performance for cattle fed 15 percent WDGS occurred when the diet contained between 1.5 percent and 2.25 percent NPN. However, removing all supplemental NPN was necessary to support optimum performance in diets containing 30 percent WCDG.