Biofuel co-products as livestock feed - Opportunities and challenges

164Biofuel co-products as livestock feed – Opportunities and challengesMAIN MESSAGES• Wheat DDGS, a co-product of the wheat ethanolindustry, contains high levels of crude protein (ca30 percent), but with a low and variable content oflysine. This variability in lysine level is dependent onthe ethanol production process and the heat damageoccurring during the DDGS drying process.• In both pigs and poultry, the ileal digestibility of lysinein DDGS is lower than in wheat, and is also quitevariable, with the lowest values in heat-damagedproducts.• Overall, heat-damaged DDGS should not be fed tonon ruminants; the dark colour of such products is anindicator of their poorer nutritional value.• The energy value of wheat DDGS for pigs or poultry islower than for wheat and is dependent mainly on theirdietary fibre content.• Standard or high quality wheat DDGS can be includedat high levels in poultry or pig diets (up to 30 percent)without marked detrimental effects on performance,as far as they are included in diets meeting the animals’overall nutrient requirements.• Overall, wheat DDGS represents a valuable sourceof energy and protein for non-ruminant animals, butattention should be paid to the variable compositionand nutritional value of DDGS when formulating diets.• Wheat (and maize) DDGS will evolve over the nearfuture, with more fractionation of the nutrients otherthan starch; an increased use of enzymes; improvementsand diversification of ethanol production technologies—allthese contributing new opportunities forfeeding pigs and poultry.TABLE 1Composition of wheat dried distillers grain with solubles (DDGS) and its comparison with wheat and maize dried distillersgrain with solublesWheat DDGS (2)Wheat (1) Maize DDGSMeanMin. – Max.(3)Dry matter (DM) 86.8 92.7 89.3 – 94.4 88.9Composition (as % of DM)Ash 1.8 5.0 4.6 – 5.7 5.8Crude protein (N×6.25) 12.1 36.6 32.7 – 39.2 30.0Crude fat 1.7 4.4 3.4 – 5.1 10.7Crude fibre 2.5 7.6 6.1 – 9.0 8.6Neutral detergent fibre (NDF) 14.3 30.1 25.4 – 35.3 41.5Acid detergent fibre (ADF) 3.6 10.7 8.1 – 13.1 16.1Acid detergent lignin (ADL) 1.2 3.2 2.1 – 4.5Starch 69.7 5.1 2.5 – 10.1 8.2Sugars 2.8 4.0 2.4 – 7.2Gross energy (MJ/kg) (4) 16.20 18.67 18.24 – 19.10 20.21Notes: (1) Sauvant, Perez and Tran, 2004. (2) n = 7; products with luminance >50; Cozannet et al., 2010a. (3) n=12, for dry matter, ash, protein, crude fat,crude fibre, NDF, ADF – Spiehs, Whitney and Shurson, 2002; n = 10, for gross energy and starch – Pedersen, Boersma and Stein, 2007. (4) Gross energy isstandardized for a 89% DM content.composition of the grain. Consequently, the nutrients,except starch, would be expected to be approximately threefold higher in wheat DDGS than those in the original grain(Table 1).However, in practice, the chemical composition of wheatDDGS is much more variable than in the original cereals,with large differences among ethanol plants according tothe method of grain preparation, namely with or withoutprevious dehulling; the fermentation process; the amountof soluble fractions blended with distillers grain; theduration and temperature of drying; and possible furtherfractionation of the non-starch fractions (separation ofproteins, etc.) (Belyea, Rausch and Tumbleson, 2004). Thereare two main technologies in use, resulting in co-productswith different starch content (Cozannet et al., 2010a). Thefirst involves entire grain grinding and fermentation, leavinga low-starch-content DDGS (7%). In addition, reflecting the technicalaspects among and within processes, the colour of DDGScan vary from light yellow to dark brown (Photo 1).Measured with a Minolta colorimeter, luminance (L)values of 10 European wheat DDGS ranged from 43 (blackproducts) to 63 (yellow products) in the study of Cozannetet al. (2010a). From their results it can be inferred thatwheat DDGS with L values