Biofuel co-products as livestock feed - Opportunities and challenges

62Biofuel co-products as livestock feed – Opportunities and challengesMAIN MESSAGES• Effects of DG on feedlot cattle performance are influencedby source and concentration of DG in the diet.• The exchange of starch for fibre plays an importantrole in digestion and animal performance as DG isadded to an SFC-based diet.• The relative difference in NEg concentration betweenDG and the basal grain it replaces provides a reasonableexplanation for differences in feedlot performanceamong different grain processing methods.• Partially replacing highly processed grain in feedlotdiets with wet DG will probably increase excretion of N,P and S, and high S concentrations might have negativeconsequences for animal health.• Implications for animal health and digestive disordersof feeding wet DG have not been extensively evaluatedand could be an important area of research.INTRODUCTIONCattle feedlots in the United States have historicallyrelied on inexpensive supplies of grain, with dietsformulated to maximize grain inclusion and limit useof more costly protein and roughage sources. In theSouthern Great Plains region, feedlots further refinedgrain utilization through extensive processing togelatinize starch, typically by steam flaking of maize andsorghum (Vasconcelos and Galyean, 2007). Expansionof fuel ethanol production in the United States viadry milling has greatly increased availability of grainbyproducts, such that distillers grains (DG; with orwithout condensed distillers solubles) are now widelyavailable in the major beef cattle feeding regions of theUnited States, including the Southern Great Plains. Fromthe standpoint of overall returns, replacing grain by DGis often economically advantageous, which has markedlyincreased the use DG in feedlot diets (Vasconcelos andGalyean, 2007). Based on research conducted in theMidwest United States, primarily with diets based onminimally processed grain (e.g. dry-rolled maize – DRC),adding DG to feedlot diets has positive effects onperformance, even at concentrations up to 50 percent ofthe dietary dry matter (DM) with wet DG (Klopfenstein,Erickson and Bremer, 2008). Because steam-flakedmaize (SFC) is the primary grain in feedlot diets in theSouthern Great Plains, and its net energy (NE) value isconsiderably greater than DRC (Zinn, Owens and Ware,2002), we embarked on a 4-year cooperative effortinvolving a consortium of 4 institutions and agenciesto evaluate utilization of wet DG in feedlot diets basedon SFC. Our objective in this review is to summarizeresearch we have conducted with feedlot cattle in ourmajor focus areas: source and concentration of DG; therole of specific nutrients and feed ingredients; potentialinteractions of grain processing and feed additives; andthe environmental impact of using wet DG in feedlotdiets in terms of nitrogen (N), phosphorus (P) andgreenhouse gas emissions.CONCENTRATION AND SOURCE OF DISTILLERSGRAINSThe effect of DG on performance seems to be influencedby both the source and concentration of DG in the diet.Klopfenstein, Erickson and Bremer (2008) presented resultsof 2 meta-analyses that suggested DG has a feeding valueas much as 78 percent greater than DRC. In contrast,values reported from research in the Southern Plains withSFC-based diets were much less, with Vasconcelos et al.(2007) reporting 12 percent decrease in gain:feed ratio(G:F) when 15 percent wet sorghum DG was included ina SFC-based diet. In our more recent work, Luebbe et al.(2010a) observed decreased G:F with incorporation of 15to 60 percent DG into SFC-based diets. Figure 1 shows thedifference in G:F response to adding wet DG to SFC-baseddiets with supplemental fat added to achieve a minimumdietary fat concentration of 6.5 percent (Luebbe et al.,2010a) compared with adding wet DG to DRC-based dietsGain:feed, g/kgFIGURE 1Gain efficiency (gain:feed)1851801751701651601551501451400 10 20 30 40 50 60 70Wet DG Inclusion, % DMNotes: Gain efficiency derives from the addition of wet distillersgrains plus solubles (DG) to steam-flaked maize-based diets inthe Southern Plains with supplemental fat added to achieve aminimum dietary fat concentration of 6.5% (Luebbe et al., 2010a;solid line) or to dry-rolled maize-based diets in the Northern Plainswith no supplemental fat (reported by Klopfenstein, Erickson andBremer,2008; dashed line).