Biofuel co-products as livestock feed - Opportunities and challenges

80Biofuel co-products as livestock feed – Opportunities and challengesTABLE 2Composition of dried distillers grains with solubles (DDGS)Parameter0 5.4Solubles level (% DM)14.5 19.1 22.1DM (%) 95.5 92.1 90.8 89.3 89.6CP (%) 32.1 31.9 31.5 30.7 30.9Fat (%) 6.9 8.9 10.4 12.7 13.3NDF (%) 36.8 34.9 31.9 30.3 29.3Notes: NDF = neutral-detergent fibre. CP = crude protein; DM = dry matter. Solubles level calculated using % NDF of solubles (2.3%) and 0% solublesDDG. Source: Adapted from Corrigan et al., 2007.were added to the grains, from 0 to 22 percent, the resultingDDGS changed from a golden yellow colour to a browncolour. However, the change in colour was not related tototal digestive tract protein digestibility because the proteinwas 97 to 98 percent digestible in all samples.Samples (n=1200) of WDGS and MDGS were collectedfor five consecutive days, across four different months andwithin six dry-milling plants, and analysed for DM, CP, fat,P and S (Buckner et al., 2011). Variation in DM contentwithin each plant was minimal (coefficient of variation (CV)less than 3 percent), but DM was different across plants.Producers should therefore be aware of the DM for eachDGS product produced, particularly when buying DGS frommore than one plant. On average, DGS contained 31.0 percentCP, 11.9 percent fat, 0.84 percent P and 0.77 percentS. Variation within days, across days, and within the sameplant remained small for CP and P (CV less than 4 percent),but P varied slightly more across plants. Fat content variationwas slightly more but remained relatively small (CV less than5 percent) within plants and within days, but larger variationwas observed among ethanol plants. Fat content variedfrom 10.9 to 13.0 percent by plant, probably due to varyingamounts of distillers solubles that the plants return to thegrains. Therefore, producers should know the fat contentfrom each plant and be less concerned with fat variationwithin a plant. Variation in S content was the largest for allnutrients tested, as CV within days and across days (withinthe same ethanol plants) ranged from 3 to 13 percent.These data suggest S values should be routinely monitoredbecause high S levels can lead to nutritional challenges.A review of several published articles summarized nutrientvariability for DGS (Benton, 2010). Average nutrientcomposition for DGS was 31.5 percent CP, 10.5 percentfat, 6 percent starch, 37.9 percent NDF, 0.51 percent P and0.57 percent S. Relatively low variation was observed for CP,NDF, P and S, with CVs of 10.7, 10.5, 8.4 and 6.3 percent,respectively. Greater variation was observed for fat andstarch, with CVs of 31.4 and 36.3 percent, respectively. Thislarge variation in fat and starch makes some logical senseas this is a summary of many samples over many ethanolplants. Not every ethanol plant combines the same proportionof distillers solubles with distillers grains, nor do theyuse the same procedure for analysing fat content. Ethanolplants are also not likely to ferment the same amount ofstarch from maize for ethanol production.Although DM variation is probably of greatest importancewith wet co-products, both fat and S levels can varyin DGS. Fat variation can lead to changes in feeding value,and S has potential for toxicity (polio encephalo malacia –PEM). It is therefore critical to have accurate analyses offeed ingredients and S analysis of the water that cattledrink. Previously, NRC suggested that diets should notexceed 0.4 percent S (NRC, 1996), or even 0.3 percent Sin high-grain feedlot diets (NRC, 2000). However, researchhas been conducted and will be presented that evaluatesperformance for cattle fed DGS diets with greater than0.4 percent S. In addition, thiamine is commonly addedat 150 to 200 mg/steer daily to offset challenges relatedto sulphur-induced PEM. This is an important issue to beaware of and to treat cattle as quickly as possible if any PEMsymptoms are observed.BEEF FINISHINGIn terms of philosophy used by nutritionists, the first units ofco-products added to a ration are primarily used to replaceprotein from urea or natural protein sources in the ration.Subsequent additions of co-products to the ration replacemaize and other grains, so are considered an energy source.Clearly, the fat and fibre in DGS is used for energy by theanimal and associated microbes when DGS is fed. In feedlotdiets with DGS at levels less than 15 to 20 percent ofdiet DM, the DGS serves to meet the protein requirementsof the animal. Conversely, when DGS is above 20 percentinclusion, the beef animal utilizes the DGS as both a proteinsource and an energy source, due to replacement of traditionalenergy sources. When protein is supplied above theanimal’s requirements, UIP that is digested is used primarilyas an energy source. Therefore, excess protein fed whenDGS inclusion is greater than 15 to 20 percent of diet DMis used as energy as well.PROTEIN SUPPLEMENTATIONIn certain production situations, light (less than 341 kg)finishing cattle may need to be supplemented with UIP (bypass)protein to meet metabolizable protein (MP) requirements.Wet or dry DGS is an excellent source of UIP.