Biofuel co-products as livestock feed - Opportunities and challenges

Nutritional value and utilization of wheat dried distillers grain with solubles in pigs and poultry 1712009), although the barley and maize contained in the dietsmight have also interacted with the multi-enzyme complexto contribute to the positive response. These results agreewith the positive effects of xylanase on nutrient digestibilityof wheat (Barrera et al., 2004) and wheat co-products fromflour milling (Yin et al., 2000; Nortey et al., 2007, 2008).For performance, enzyme effects depend on numerousparameters (Adeola and Cowieson, 2011). The studyof Emiola et al. (2009) suggests a global improvement ofperformance in animals fed wheat DDGS diets. This positiveeffect of enzymes supplementation is consistent withthe results of Wang et al. (2009), Jones et al. (2010) orPéron, Plumstead and Moran (2009) with pig diets andOlukosi, Cowieson and Adeola (2010) in poultry diets. Incontrast, a meta-analysis carried out by Jacela et al. (2009)involving 4506 pigs (4 trials) and different enzyme typessuggests no beneficial effect of enzymes in maize-soybeanmeal diets containing up to 60 percent maize DDGS. Theselatter results are corroborated by Widyaratne, Patience andZijlstra (2009).KNOWLEDGE GAPS AND FUTURE RESEARCHNEEDSWheat and maize DDGS are produced after a series ofoperations, the last being drying the product for its conservation,transportation and inclusion in dry compoundfeeds. In these stages of the process, and especially duringthe last stage, proteins and carbohydrates interact with theproduction of Amadori compounds generated by Maillardreactions. A major impact concerns the lysine fraction ofthe proteins, which can be destroyed or, at least, blockedand become unavailable for digestion. A major area ofresearch would consist in producing methods for characterizingthese compounds, studying their impact on the physicaland nutritional parameters of wheat (and maize) DDGS,and proposing methods for a rapid and simple predictionof the nutritional value of DDGS, in addition to the classicalprediction methods based on crude nutrients. This wouldalso help the ethanol plants to optimize and standardizetheir procedures, not only for ethanol yield but also accordingto the nutritional value of their co-products (Oryschaket al., 2010b). The important effects of drying on productphysical properties and nutritional value also suggest thepotential of infrared technologies as a quick and reliabletool for DDGS evaluation. This work has been startedand is promising, but it still requires additional data for itscomplete achievement. In addition, the full potential of thisraw material should be evaluated according to its propernutritional values under a least-cost formulation constraintfor diets fed to different animal species and stages ofproduction. Environmental impact of biofuels productionrequires further work, as anticipated by Jarret et al. (2011)and Jarret, Martinez and Dourmad (2011) in terms of slurryproperties, methane production and carbon footprint ofDDGS used as animal feed. Further research would alsobe required for phosphorus evaluation (Widyaratne andZijlstra, 2009), which review also pointed out a lack of referencesin the field of micronutrient and vitamin contents inwheat DDGS. The impact of wheat DDGS on the gut healthof pigs and poultry should also be investigated in orderto have a full overview of wheat DDGS potential in pigand poultry production. Finally, the production of ethanolfrom cereals will probably change in the near future due tofractionation of residues in order to produce protein-, fat-,DF- or micro-constituents-rich fractions, with consequentmajor changes in the composition of DDGS. This impliesthat DDGS characteristics for pigs and poultry nutrition willneed to be defined precisely.CONCLUSIONSThis review shows that wheat DDGS are a potential sourceof energy, protein and phosphorus for poultry and pig diets.However, nutritionists using DDGS in diets for monogastricspecies should be aware of the current variability innutrient content and digestibility. Colour score appearsto be a promising method for a rapid and reliable estimationof both energy and amino acids digestibility, or, atleast, a rapid classification method of DDGS usable fornon-ruminant animals. In practice, a better knowledge ofproduct quality might prevent any detrimental effect inanimals fed DDGS and allow higher inclusion levels. Ourreview also suggests that the processing of DDGS should beadapted and optimized in order to obtain a high quality coproduct.Finally, quality and uniformity improvement mightbe expected for DDGS in the future, but there will also bediversification of the co-products with the production ofmore specific co-products (with or without hulls; proteinconcentrations; germ separation; etc.).ACKNOWLEDGEMENTSThe authors would thank C. Gady and P.A. Geraert(Adisseo), Y. Jaguelin and M. Lessire (INRA), L. Le Tutour andY. Primot (Ajinomoto Eurolysine) and J.P. Métayer (Arvalis-Institut du végétal) for their active contribution in many ofthe results used in this review.BIBLIOGRAPHYAdeola, O. & Cowieson, A.J. 2011. Board invited review:Opportunities and challenges in using exogenous enzymesto improve non-ruminant animal production. Journal ofAnimal Science, 89: 3189–3218.Adeola, O., Jendza, J.A., Southern, L.L., Powell, S. &Owusu-Asiedu, A. 2010. Contribution of exogenousdietary carbohydrases to the metabolizable energy value ofcorn distillers grains for broiler chickens. Poultry Science,89: 1947–1954.