Biofuel co-products as livestock feed - Opportunities and challenges

61Chapter 4Utilization of wet distillers grains inhigh-energy beef cattle diets based onprocessed grainM.L. Galyean, 1, 5 N.A. Cole, 2 M.S. Brown, 3, 4 J.C. MacDonald, 3, 4 C.H. Ponce 1 and J.S. Schutz 11Department of Animal and Food Sciences, Texas Tech University, Box 42141, Lubbock 79409, United States of America2USDA-ARS-CPRL 1 , Bushland, TX 79012, United States of America3West Texas A&M University, Canyon 79016, United States of America4Texas AgriLife Research, Amarillo 79106, United States of AmericaCorresponding author e-mail: michael.galyean@ttu.eduABSTRACTDistillers grains (DG) are used extensively by beef cattle feeding operations in the United States, including theSouthern Great Plains. Our regional research consortium has conducted research focused on utilization of wet DGin feedlot diets based on steam flaked maize (SFC). Effects of DG on feedlot cattle performance are influencedby source and concentration of DG in the diet. In SFC-based diets, DG concentrations of 15 to 60 percent in thedry matter (DM) decreased gain efficiency, with effects seemingly related to the neutral-detergent fibre (NDF)content of wet DG and associated changes in ruminal DM and NDF digestibility. Thus, the exchange of starch forfibre plays an important role in digestion and animal performance as DG is added to a SFC-based diet. Wet DGcontributes a unique source of fat to the diet; however, our findings indicate that fat contained in sorghum DGand in a commonly used commercial source (yellow grease – an animal-vegetable fat blend) are utilized in a similarmanner. Exchanging DG for SFC and oilseed meals typically decreases degradability of crude protein (CP) andoften increases the total dietary CP. Our results indicated that between 0.52 and 0.78 percent urea was needed tooptimize feedlot performance with diets containing 15 percent wet DG, but added urea was not beneficial whenthe diet contained 30 percent DG, presumably reflecting recycling of excess CP in 30 percent DG diets. Althoughinteractions between DG concentration and grain processing method have been reported, our results with SFC- vsdry-rolled maize-based diets have not provided evidence of an interaction. The relative difference in net energy forgain (NEg) concentration between DG and the basal grain it replaces seems to provide a reasonable explanation fordifferences in feedlot performance when DG is fed with different processed grains. High concentrations of sulphur(S) and their effects on health and performance of feedlot cattle are a practical concern when including DG infeedlot diets. In our work, feed additives like ionophores and antibiotics did not increase in vitro ruminal hydrogensulphide, but H 2 S production was clearly responsive to dietary S concentration. Manure production varies withthe concentration of DG in the diet, basal grain processing method, and other dietary ingredients. The quantityof manure collected and the phosphorus (P) excreted in manure from feedlot pens increases with addition of DGto finishing diets. When applied to meet crop P requirements, farmland required to utilize the manure increasesapproximately 20 percent for each 10 percent increase in wet DG in the diet. Greenhouse gas emissions fromfeedlots using DG are variable and need further study. Overall, our results suggest that DG can be a useful sourceof energy and protein in feedlot diets, but optimal concentrations of DG are less in SFC-based diets than in dietsbased on minimally processed maize.1The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age,disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs,reprisal, or because all or part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.)Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contactUSDA’s TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400Independence Avenue, S.W., Washington, D.C. 20250-9410, or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunityprovider and employer.