Substitution of wheat dried distillers grains with solubles for barley grain or barley silage in feedlot cattle diets: Intake, digestibility, and ruminal fermentation 1 Y. L. Li,*† T. A. McAllister,* K. A. Beauchemin,* M. L. He,* J. J. McKinnon,‡ and W. Z. Yang* 2 *Research Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta, T1J 4B1, Canada; †Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China; and ‡Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A8, Canada ABSTRACT: The objective of this study was to evaluate the effects of substituting wheat dried distill- ers grains with solubles (DDGS) for barley grain and barley silage on intake, digestibility, and ruminal fer- mentation in feedlot beef cattle. Eight ruminally can- nulated Angus heifers (initial BW 455 ± 10.8 kg) were assigned to a replicated 4 × 4 Latin square design with 4 treatments: control, low (25%), medium (30%), and high (35%) wheat DDGS (DM basis). The diets con- sisted of barley silage, barley concentrate, and wheat DDGS in ratios of 15:85:0 (CON), 10:65:25 (25DDGS), 5:65:30 (30DDGS), and 0:65:35 (35DDGS; DM basis), respectively. The diets were formulated such that wheat DDGS was substituted for both barley grain and barley silage to evaluate whether wheat DDGS can be fed as a source of both energy (grain) and fiber in feedlot finish- ing diets. Intakes (kg/d) of DM and OM were not dif- ferent, whereas those of CP, NDF, ADF, and ether ex- tract (EE) were greater (P < 0.01) and intake of starch was less (P < 0.01) for the 25DDGS compared with the CON diet. The digestibilities of CP, NDF, ADF, and EE in the total digestive tract were greater (P < 0.05) for 25DDGS vs. CON. Ruminal pH and total VFA concentrations were not different (P > 0.15) between 25DDGS and CON diets. Replacing barley silage with increasing amounts of wheat DDGS (i.e., from 25DDGS to 35DDGS) linearly reduced (P < 0.05) intakes of DM and other nutrients without altering (P = 0.40) CP intake. In contrast, digestibilities of DM and other nu- trients in the total digestive tract linearly increased (P < 0.05) with increasing wheat DDGS except for that of EE. Additionally, with increasing amounts of wheat DDGS, mean ruminal pH tended (P = 0.10) to linearly decrease, and ruminal pH status decreased with longer (P = 0.04) duration of pH <5.5 and <5.2, and greater (P = 0.01) curve area under pH <5.8 and <5.5 without altering (P > 0.19) ruminal VFA and NH 3 -N concen- trations. Results indicated that wheat DDGS can be effectively used to replace both barley grain and silage at a moderate amount to meet energy and fiber require- ments of finishing cattle. However, when silage content of the diet is low (<10%), wheat DDGS is not an effec- tive fiber source, so replacing forage fiber with wheat DDGS in finishing diets decreases overall ruminal pH status even though the rapidly fermentable starch con- tent of the diet is considerably reduced. Key words: beef cattle, digestibility, intake, ruminal fermentation, wheat dried distillers grain with solubles ©2011 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2011. 89:2491–2501 doi:10.2527/jas.2010-3418 INTRODUCTION Expansion of fuel ethanol production in North Amer- ica has resulted in a significant increase in the use of distillers grains (DG) in the diets of feedlot cattle. Corn DG has been used for many years in both beef and dairy cattle rations, and its nutritional character- istics and feeding value have been well documented (Klopfenstein et al., 2008; Schingoethe et al., 2009). In western Canada, wheat has also been explored as a substrate for ethanol production, but only a limit- ed amount of research has been conducted to deter- mine the value of wheat-based dried DG with solubles 1 Contribution number: 38710041. This study was conducted with funding from the Canadian Cattlemen’s Association (Calgary), Alberta Beef Producers (Edmonton), Alberta Livestock and Meat Agency Ltd. (Edmonton), and Natural Sciences and Engineering Research Council of Canada (Ottawa). The authors thank the Leth- bridge Research Centre barn staff for their care and management of the animals, and Karen Andrews, Alastair Furtado, Heather Pirot, Bev Farr, and Darrell Vedres for their technical assistance. 2 Corresponding author: wenzhu.yang@agr.gc.ca Received August 10, 2010. Accepted March 14, 2011. 2491 Published December 4, 2014