Biofuel co-products as livestock feed - Opportunities and challenges

Feeding biofuel co-products to dairy cattle 117TABLE 2Composition of different cereal grainsMaize Sorghum Wheat Barley Triticale RyeNutrients (% of DM)NDF 9.9 ± 1.3 13.8 ± 6.2 12.9 ± 1.1 19.8 ± 1.6 14.3 ± 0.2 16.5 ± 2.3ADF 3.5 ± 0.4 5.2 ± 0.9 4.0 ± 0.4 6.9 ± 0.4 3.9 ± 0.2 5.2 ± 2.4Lignin 0.7 ± 0.4 1.1 ± 0.3 1.2 ± 0.4 1.8 ± 0.4 1.1 ± 0.2 1.1 ± 0.1Starch 73.8 ± 1.0 67.7 ± 9.9 66.9 ± 2.3 57.0 ± 2.8 64.9 ± 3.4 59.8 ± 1.9CP 9.1 ± 0.3 10.9 ± 0.7 13.2 ± 1.1 12.3 ± 0.5 12.4 ± 1.2 11.1 ± 1.8Crude fat 4.5 ± 0.6 3.3 ± 0.3 2.0 ± 0.2 2.1 ± 0.1 1.7 ± 0.1 1.6 ± 0.2Ash 1.50 ± 0.08 1.8 ± 0.26 1.9 ± 0.1 2.9 ± 0.3 2.0 ± 0.1 1.9 ± 0.2Ca 0.04 ± 0.01 0.04 ± 0.02 0.06 ± 0.02 0.07 ± 0.01 0.07 ± 0.01 0.07 ± 0.03P 0.24 ± 0.13 0.34 ± 0.01 0.40 ± 0.03 0.41 ± 0.03 0.37 ± 0.03 0.36 ± 0.02S 0.13 ± 0.02 0.11 ± 0.01 0.26 ± 0.19 0.14 ± 0.02 0.16 ± 0.01 0.14 ± 0.04Energy parameters (Mcal/kg)NEM 2.13 ± 0.05 1.98 ± 0.04 2.11 ± 0.06 2.15 ± 0.18 2.01 2.02NEG 1.45 ± 0.04 1.31 ± 0.01 1.45 ± 0.03 1.35 ± 0.01 1.37 1.34NEL 1.97 ± 0.15 1.85 ± 0.09 1.91 ± 0.16 1.80 ± 0.17 1.85 ± 0.20 1.89 ± 0.12Notes: Nutrients: NDF = neutral-detergent fibre; ADF = acid-detergent fibre; CP = crude protein. Energy parameters: NEM = net energy formaintenance; NEG = net energy for gain; and NEL = net energy for lactation. Data are reported as means ± the standard deviation.Sources: Adapted from NRC, 2001; FEDNA, 2003; INRA, 2004; CNCPS, 2009.most resistant to microbial fermentation (FEDNA, 2003).Consequently, this results in the lowest effective proteindegradability of all cereal grains (INRA, 2004). Its concentrationof starch and fat (67.7 and 3.3 percent, respectively)are slightly less than that of maize, which, together withgreater fibre concentration, results in a lower net energy forlactation (NEL) content (1.85 Mcal/kg NEL) compared withmaize DGS (1.97 Mcal/kg NEL).Although with great variability between experiments,there has been more CP reported in sorghum DGS comparedwith maize DGS (34.1 vs 31.2 percent; Table 3), witha range between 24.4 and 45 percent. These variationswere also observed among DGS produced in the sameplant, albeit with different moisture contents. Depenbuschet al. (2009) reported CP contents of 45 percent for dried(92 percent DM) and 34 percent wet (36 percent DM)sorghum DGS. In the same experiment, however, the CPconcentration between wet and dried maize DGS varied byonly 3 percent.The average fat values in sorghum DGS studied weresimilar to that of maize (11.3 vs 11.9 percent) in spite ofa 26 percent lower fat content in sorghum than maize,which resulted in similar NEL values between both typesof DGS (2.24 Mcal/kg). The percentage of starch and aciddetergentfibre (ADF) of sorghum DGS were greater thanin maize DGS as a result of the greater resistance to degradationof the protein matrix that encapsulates the starchgranules of the sorghum endosperm.Wang et al. (2008) compared ethanol production characteristicsof 70 sorghum varieties with different nutrientcomposition and physical properties. The average starchcontent varied between 64 and 74 percent, and had anefficiency of conversion to ethanol of 86 to 93.8 percent.The authors also determined that variations in ethanolyields could be as high as 7.4 percent, particularly due tonegative effects on fermentation efficiency caused by highamylose concentration in some varieties. There were nosignificant differences due to grain colour, except for browntannin-containing varieties. Results with those varietiesconfirmed that high-tannin genetic lines are not suitablefor ethanol production. These experiments demonstrate theimportance for ethanol plants of adequate selection of thesubstrate to be used for fermentation. The darker colour ofsorghum DGS, often mistakenly identified with excessiveheating during drying (Maillard reaction), is frequently dueto the darker colour of the variety of sorghum, which canreduce their acceptability in the market.Wheat distillers grainWheat is considered as one of the main ethanol-producingcrops in the EU (FAOSTAT data) with almost one-third ofthe bio-refineries using it as the sole substrate (Table 1). InNorth America, western Canada produces over 500 millionlitres of ethanol each year from over 1.3 million tonnes ofwheat or wheat-maize blends (University of Saskatchewan,2009). Half of the bio-refineries located in Canada, usewheat as the sole substrate or together with other cerealgrains (Table 1). In contrast, the United States has only oneethanol plant that uses wheat as part of its substrates,located in Texas (RFA, 2011).Wheat is classified as hard or soft, depending on thephysical hardness of the endosperm and its resistanceto grinding (Hruskova and Svec, 2009; Saunders, 2009).Grain hardness does not affect ethanol yield (Swanston etal., 2007), but wheat varieties with harder endosperm areassociated with processing problems (Dexter and Edwards,