Biofuel co-products as livestock feed - Opportunities and challenges

404Biofuel co-products as livestock feed – Opportunities and challengesMAIN MESSAGES• DDGS from fuel ethanol production can be an effectiveprotein ingredient in aquafeeds.• DDGS serves to replace SBM and maize in the diet, butnot fish meal.• For most fish species, a level of 20% DDGS appearsto be the maximum inclusion if supplemental lysineis not added.• If supplemental lysine is used, maximum DDGS levelsgreater than 20% can be used.• Crude glycerine from biodiesel production appears tobe a potential energy source.• Much work needs to be conducted on use of glycerinin fish diets.FIGURE 1Production and exports of distillers dried grains with solubles (DDGS) from the United Statesdry-grind fuel ethanol industry35DDGS (tonnes) x 10 63025201510ProductionExport501992/931993/941994/951995/961996/971997/981998/991999/002000/012001/022002/032003/042004/052005/062006/072007/082008/092009/102010/11Source: Adapted from Hoffman and Baker, 2010.Marketing yearand fish oil. Fish meal used in aquaculture represented68.2 percent of total global fish meal production in 2006(Tacon and Metian, 2008), but increased pressure dueto exploiting marine resources and rising prices couldultimately decrease the use of fish meal, as it will inevitablybe replaced by less expensive alternative proteins.DDGS, a relatively cheap protein source (Figure 3) comparedwith fish meal, is a candidate plant protein. Duringthe last 10 years, DDGS market price has been generallybetween 5 percent and 20 percent that of fish meal. WhileDDGS is not recommended as a direct, complete replacementfor fish meal, it can be used with, or in lieu of, otherplant proteins (such as soybean meal – SBM) to reduce theuse of fish meal in aquafeeds. As shown in Figure 3, overthe last decade the price of DDGS has ranged from approximately20 percent to 70 percent that of SBM.This chapter will review the nutrient composition ofmajor biofuels (i.e. maize-based fuel ethanol and soy-basedbiodiesel) co-products (i.e. distillers grain and crude glycerin),will provide summaries of available nutritional studiesfor different fish species, and will conclude with finalremarks on challenges associated with these co-productsand areas of needed research.Before proceeding, however, it is important to note afew key issues. First, maize is the primary feedstock for fuelethanol production in the United States. Other starch-richmaterials can theoretically also be used to produce ethanol,including barley, cassava, field peas, millet, triticale, oats,rice, rye, sorghum, sweet potato and wheat. Unfortunately,most of these alternative starch sources have only beeninvestigated on a laboratory- or pilot-scale and are notreadily commercially available. Not surprisingly, fish feedingtrials are essentially non-existent for co-products from thesesubstrates, and thus will not be discussed in this chapter.In contrast, biodiesel can be produced from a varietyof oilseeds and lipid-containing materials, including canola